diff --git a/.playwright-mcp/console-2026-02-12T09-06-28-438Z.log b/.playwright-mcp/console-2026-02-12T09-06-28-438Z.log
new file mode 100644
index 0000000..ab04aa5
--- /dev/null
+++ b/.playwright-mcp/console-2026-02-12T09-06-28-438Z.log
@@ -0,0 +1 @@
+[    7988ms] [ERROR] Failed to load resource: the server responded with a status of 404 (Not Found) @ http://localhost:5173/favicon.ico:0
diff --git a/PROGRESS.md b/PROGRESS.md
index 3dc67e0..f94e4bd 100644
--- a/PROGRESS.md
+++ b/PROGRESS.md
@@ -1,7 +1,7 @@
 # Synthesis — Development Progress
 
 > **Last updated:** 2026-02-12  
-> **Current phase:** Phase 0 ✅ → Ready for Phase 1
+> **Current phase:** Phase 1 ✅ → Ready for Phase 2
 
 ---
 
@@ -19,23 +19,32 @@
 - [x] Implementation plan (`IMPLEMENTATION-PLAN.md`)
 - [x] Progress tracking (this file)
 
+### Phase 1: Chemistry Engine ✅
+- [x] 1.1 Types and interfaces (`src/chemistry/types.ts`)
+- [x] 1.2 Element data — 20 real elements (`src/data/elements.json`)
+- [x] 1.3 Element registry with lookup by symbol/number (`src/chemistry/elements.ts`)
+- [x] 1.4 Reaction engine — O(1) lookup, condition checking, failure reasons (`src/chemistry/engine.ts`)
+- [x] 1.5 Reaction data — 34 real reactions (`src/data/reactions.json`)
+- [x] 1.6 Compound data — 25 compounds with game effects (`src/data/compounds.json`)
+- [x] 1.7 Unit tests — 35 passing (`tests/chemistry.test.ts`)
+
 ---
 
 ## In Progress
 
-_None — ready to begin Phase 1_
+_None — ready to begin Phase 2_
 
 ---
 
-## Up Next: Phase 1 — Chemistry Engine
+## Up Next: Phase 2 — ECS Foundation
 
-- [ ] 1.1 Types and interfaces (`Element`, `Reaction`, `Compound`)
-- [ ] 1.2 Element data — 20 real elements (JSON)
-- [ ] 1.3 Element registry with lookup
-- [ ] 1.4 Reaction engine core
-- [ ] 1.5 Reaction data — 50 real reactions (JSON)
-- [ ] 1.6 Compound properties
-- [ ] 1.7 Unit tests (vitest)
+- [ ] 2.1 World setup (bitECS world + time tracking)
+- [ ] 2.2 Core components (Position, Velocity, SpriteRef, Health)
+- [ ] 2.3 Movement system
+- [ ] 2.4 Phaser ↔ bitECS sync bridge
+- [ ] 2.5 Entity factory
+- [ ] 2.6 Health/damage system
+- [ ] 2.7 Visual test (entities moving on screen)
 
 ---
 
@@ -49,4 +58,5 @@ None
 
 | # | Date | Phase | Summary |
 |---|------|-------|---------|
-| 1 | 2026-02-12 | Phase 0 | Project setup complete: GDD, engine analysis, npm init, Phaser config, BootScene, cursor rules, implementation plan |
+| 1 | 2026-02-12 | Phase 0 | Project setup: GDD, engine analysis, npm init, Phaser config, BootScene, cursor rules, plan |
+| 2 | 2026-02-12 | Phase 1 | Chemistry engine: 20 elements, 25 compounds, 34 reactions, engine with O(1) lookup + educational failures, 35 tests passing |
diff --git a/boot-screen.png b/boot-screen.png
new file mode 100644
index 0000000..c5fa8f5
Binary files /dev/null and b/boot-screen.png differ
diff --git a/src/chemistry/compounds.ts b/src/chemistry/compounds.ts
new file mode 100644
index 0000000..1560825
--- /dev/null
+++ b/src/chemistry/compounds.ts
@@ -0,0 +1,35 @@
+import type { CompoundData } from './types';
+import compoundsRaw from '../data/compounds.json';
+
+const compounds: CompoundData[] = compoundsRaw as CompoundData[];
+
+const byId = new Map<string, CompoundData>();
+
+for (const c of compounds) {
+  if (byId.has(c.id)) {
+    throw new Error(`Duplicate compound id: ${c.id}`);
+  }
+  byId.set(c.id, c);
+}
+
+export const CompoundRegistry = {
+  getById(id: string): CompoundData | undefined {
+    return byId.get(id);
+  },
+
+  getAll(): readonly CompoundData[] {
+    return compounds;
+  },
+
+  has(id: string): boolean {
+    return byId.has(id);
+  },
+
+  count(): number {
+    return compounds.length;
+  },
+
+  isCompound(id: string): boolean {
+    return byId.has(id);
+  },
+} as const;
diff --git a/src/chemistry/elements.ts b/src/chemistry/elements.ts
new file mode 100644
index 0000000..8e890fa
--- /dev/null
+++ b/src/chemistry/elements.ts
@@ -0,0 +1,45 @@
+import type { ElementData } from './types';
+import elementsRaw from '../data/elements.json';
+
+const elements: ElementData[] = elementsRaw as ElementData[];
+
+const bySymbol = new Map<string, ElementData>();
+const byNumber = new Map<number, ElementData>();
+
+for (const el of elements) {
+  if (bySymbol.has(el.symbol)) {
+    throw new Error(`Duplicate element symbol: ${el.symbol}`);
+  }
+  if (byNumber.has(el.atomicNumber)) {
+    throw new Error(`Duplicate atomic number: ${el.atomicNumber}`);
+  }
+  bySymbol.set(el.symbol, el);
+  byNumber.set(el.atomicNumber, el);
+}
+
+export const ElementRegistry = {
+  getBySymbol(symbol: string): ElementData | undefined {
+    return bySymbol.get(symbol);
+  },
+
+  getByNumber(num: number): ElementData | undefined {
+    return byNumber.get(num);
+  },
+
+  getAll(): readonly ElementData[] {
+    return elements;
+  },
+
+  has(symbol: string): boolean {
+    return bySymbol.has(symbol);
+  },
+
+  count(): number {
+    return elements.length;
+  },
+
+  /** Check if a symbol is an element (vs compound) */
+  isElement(id: string): boolean {
+    return bySymbol.has(id);
+  },
+} as const;
diff --git a/src/chemistry/engine.ts b/src/chemistry/engine.ts
new file mode 100644
index 0000000..7bcfebf
--- /dev/null
+++ b/src/chemistry/engine.ts
@@ -0,0 +1,209 @@
+import type { Reactant, ReactionData, ReactionResult, ReactionConditions } from './types';
+import { ElementRegistry } from './elements';
+import { CompoundRegistry } from './compounds';
+import reactionsRaw from '../data/reactions.json';
+
+const reactions: ReactionData[] = reactionsRaw as ReactionData[];
+
+// === Reaction Key: sorted "id:count" pairs joined by "+" ===
+
+function makeReactionKey(reactants: Reactant[]): string {
+  return reactants
+    .map((r) => `${r.id}:${r.count}`)
+    .sort()
+    .join('+');
+}
+
+// Build index for O(1) lookup
+const reactionIndex = new Map<string, ReactionData>();
+
+for (const r of reactions) {
+  const key = makeReactionKey(r.reactants);
+  if (reactionIndex.has(key)) {
+    console.warn(`Duplicate reaction key: ${key} (${r.id} conflicts with ${reactionIndex.get(key)!.id})`);
+  }
+  reactionIndex.set(key, r);
+}
+
+// === Failure Reason Generation ===
+
+function isNobleGas(id: string): boolean {
+  const el = ElementRegistry.getBySymbol(id);
+  return el?.category === 'noble-gas';
+}
+
+function generateFailureReason(
+  reactants: Reactant[],
+  conditions?: Partial<ReactionConditions>,
+): { reason: string; reasonRu: string } {
+  const ids = reactants.map((r) => r.id);
+
+  // Check for noble gas
+  const nobleGas = ids.find((id) => isNobleGas(id));
+  if (nobleGas) {
+    const el = ElementRegistry.getBySymbol(nobleGas)!;
+    return {
+      reason: `${el.name} is a noble gas — it has a full electron shell and refuses to react with anything.`,
+      reasonRu: `${el.nameRu} — благородный газ с полной электронной оболочкой. Не реагирует ни с чем.`,
+    };
+  }
+
+  // Check if all inputs are the same element
+  const uniqueIds = new Set(ids);
+  if (uniqueIds.size === 1) {
+    return {
+      reason: `Cannot react an element with itself under these conditions. Try combining with a different element.`,
+      reasonRu: `Нельзя провести реакцию элемента с самим собой в этих условиях. Попробуйте другой элемент.`,
+    };
+  }
+
+  // Check for gold (extremely unreactive)
+  if (ids.includes('Au')) {
+    return {
+      reason: `Gold is extremely unreactive — it resists most chemical attacks. Only aqua regia (HNO₃ + HCl) can dissolve it.`,
+      reasonRu: `Золото крайне инертно — устойчиво к большинству реагентов. Только царская водка (HNO₃ + HCl) растворяет его.`,
+    };
+  }
+
+  // Check if a matching reaction exists but conditions aren't met
+  const key = makeReactionKey(reactants);
+  // Try nearby keys (different counts)
+  for (const [rKey, reaction] of reactionIndex) {
+    const rIds = new Set(reaction.reactants.map((r) => r.id));
+    const inputIds = new Set(ids);
+    if (setsEqual(rIds, inputIds) && rKey !== key) {
+      return {
+        reason: `These elements can react, but you need different proportions. Check the amounts carefully.`,
+        reasonRu: `Эти элементы могут реагировать, но нужны другие пропорции. Проверьте количества.`,
+      };
+    }
+  }
+
+  // Default
+  return {
+    reason: `No known reaction between these substances under current conditions. Try adding heat, a catalyst, or different elements.`,
+    reasonRu: `Нет известной реакции между этими веществами в текущих условиях. Попробуйте нагрев, катализатор или другие элементы.`,
+  };
+}
+
+function setsEqual<T>(a: Set<T>, b: Set<T>): boolean {
+  if (a.size !== b.size) return false;
+  for (const item of a) {
+    if (!b.has(item)) return false;
+  }
+  return true;
+}
+
+// === Condition Checking ===
+
+function checkConditions(
+  required: ReactionConditions | undefined,
+  provided: Partial<ReactionConditions> | undefined,
+): { met: boolean; reason?: string; reasonRu?: string } {
+  if (!required) return { met: true };
+
+  if (required.minTemp && (!provided?.minTemp || provided.minTemp < required.minTemp)) {
+    return {
+      met: false,
+      reason: `This reaction requires a temperature of at least ${required.minTemp}°. You need a heat source.`,
+      reasonRu: `Эта реакция требует температуру не менее ${required.minTemp}°. Нужен источник тепла.`,
+    };
+  }
+
+  if (required.catalyst) {
+    const catalystName =
+      ElementRegistry.getBySymbol(required.catalyst)?.name ??
+      CompoundRegistry.getById(required.catalyst)?.name ??
+      required.catalyst;
+
+    if (!provided?.catalyst || provided.catalyst !== required.catalyst) {
+      return {
+        met: false,
+        reason: `This reaction requires a catalyst: ${catalystName}. The catalyst is not consumed — it just enables the reaction.`,
+        reasonRu: `Эта реакция требует катализатор: ${catalystName}. Катализатор не расходуется — он лишь запускает реакцию.`,
+      };
+    }
+  }
+
+  if (required.requiresEnergy && !provided?.requiresEnergy) {
+    return {
+      met: false,
+      reason: `This reaction requires an external energy source (e.g., electricity). It's endothermic — it absorbs energy.`,
+      reasonRu: `Эта реакция требует внешний источник энергии (напр., электричество). Она эндотермическая — поглощает энергию.`,
+    };
+  }
+
+  return { met: true };
+}
+
+// === Public API ===
+
+export const ReactionEngine = {
+  /**
+   * Attempt a reaction with given reactants and conditions.
+   * Returns success with products, or failure with educational reason.
+   */
+  react(
+    reactants: Reactant[],
+    conditions?: Partial<ReactionConditions>,
+  ): ReactionResult {
+    // Validate all inputs exist
+    for (const r of reactants) {
+      if (!ElementRegistry.isElement(r.id) && !CompoundRegistry.isCompound(r.id)) {
+        return {
+          success: false,
+          failureReason: `Unknown substance: "${r.id}". Check spelling.`,
+          failureReasonRu: `Неизвестное вещество: "${r.id}". Проверьте написание.`,
+        };
+      }
+    }
+
+    const key = makeReactionKey(reactants);
+    const reaction = reactionIndex.get(key);
+
+    if (!reaction) {
+      const { reason, reasonRu } = generateFailureReason(reactants, conditions);
+      return {
+        success: false,
+        failureReason: reason,
+        failureReasonRu: reasonRu,
+      };
+    }
+
+    // Check conditions
+    const condCheck = checkConditions(reaction.conditions, conditions);
+    if (!condCheck.met) {
+      return {
+        success: false,
+        failureReason: condCheck.reason,
+        failureReasonRu: condCheck.reasonRu,
+      };
+    }
+
+    return {
+      success: true,
+      products: reaction.products,
+      reaction,
+    };
+  },
+
+  /** Get a reaction by its ID */
+  getById(id: string): ReactionData | undefined {
+    return reactions.find((r) => r.id === id);
+  },
+
+  /** Get all known reactions */
+  getAll(): readonly ReactionData[] {
+    return reactions;
+  },
+
+  /** Get the number of registered reactions */
+  count(): number {
+    return reactions.length;
+  },
+
+  /** Build a reaction key from reactants (for testing/debugging) */
+  makeKey(reactants: Reactant[]): string {
+    return makeReactionKey(reactants);
+  },
+} as const;
diff --git a/src/chemistry/types.ts b/src/chemistry/types.ts
new file mode 100644
index 0000000..3c098af
--- /dev/null
+++ b/src/chemistry/types.ts
@@ -0,0 +1,102 @@
+// === Element Types ===
+
+export type ElementCategory =
+  | 'alkali-metal'
+  | 'alkaline-earth'
+  | 'transition-metal'
+  | 'post-transition-metal'
+  | 'metalloid'
+  | 'nonmetal'
+  | 'halogen'
+  | 'noble-gas';
+
+export type MatterState = 'solid' | 'liquid' | 'gas';
+
+export interface ElementData {
+  symbol: string;
+  name: string;
+  nameRu: string;
+  atomicNumber: number;
+  atomicMass: number;
+  electronegativity: number; // 0 for noble gases
+  category: ElementCategory;
+  state: MatterState; // at room temperature
+  color: string; // hex for rendering
+  description: string;
+  descriptionRu: string;
+}
+
+// === Compound Types ===
+
+export interface CompoundData {
+  id: string; // lookup key, e.g. "NaCl"
+  formula: string; // display formula with Unicode, e.g. "NaCl"
+  name: string;
+  nameRu: string;
+  mass: number; // molecular mass
+  state: MatterState;
+  color: string;
+  properties: CompoundProperties;
+  description: string;
+  descriptionRu: string;
+  gameEffects: string[];
+}
+
+export interface CompoundProperties {
+  flammable: boolean;
+  toxic: boolean;
+  explosive: boolean;
+  acidic: boolean;
+  basic: boolean;
+  oxidizer: boolean;
+  corrosive: boolean;
+}
+
+// === Reaction Types ===
+
+export type ReactionType =
+  | 'synthesis'
+  | 'decomposition'
+  | 'combustion'
+  | 'single-replacement'
+  | 'double-replacement'
+  | 'acid-base'
+  | 'redox';
+
+export interface Reactant {
+  id: string; // element symbol or compound id
+  count: number;
+}
+
+export interface Product {
+  id: string; // element symbol or compound id
+  count: number;
+}
+
+export interface ReactionConditions {
+  minTemp?: number; // 0=room, 100=boiling, 500=fire, 1000=furnace
+  catalyst?: string; // compound id required as catalyst
+  requiresEnergy?: boolean; // needs external energy (electricity)
+}
+
+export interface ReactionData {
+  id: string;
+  reactants: Reactant[];
+  products: Product[];
+  conditions?: ReactionConditions;
+  energyChange: number; // -100..+100, negative = exothermic
+  type: ReactionType;
+  description: string;
+  descriptionRu: string;
+  difficulty: number; // 1-5
+}
+
+// === Engine Result ===
+
+export interface ReactionResult {
+  success: boolean;
+  products?: Product[];
+  reaction?: ReactionData;
+  failureReason?: string;
+  failureReasonRu?: string;
+}
diff --git a/src/data/compounds.json b/src/data/compounds.json
new file mode 100644
index 0000000..fa4c0f5
--- /dev/null
+++ b/src/data/compounds.json
@@ -0,0 +1,202 @@
+[
+  {
+    "id": "H2O", "formula": "H₂O", "name": "Water", "nameRu": "Вода",
+    "mass": 18.015, "state": "liquid", "color": "#4488cc",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Universal solvent. Essential for life and countless reactions.",
+    "descriptionRu": "Универсальный растворитель. Необходима для жизни и бесчисленных реакций.",
+    "gameEffects": ["hydration", "cooling", "solvent"]
+  },
+  {
+    "id": "NaCl", "formula": "NaCl", "name": "Sodium Chloride", "nameRu": "Поваренная соль",
+    "mass": 58.44, "state": "solid", "color": "#f0f0f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Table salt. Preserves food via osmosis. Essential electrolyte.",
+    "descriptionRu": "Поваренная соль. Консервирует пищу через осмос. Необходимый электролит.",
+    "gameEffects": ["preservation", "trade", "slug_repellent"]
+  },
+  {
+    "id": "CO2", "formula": "CO₂", "name": "Carbon Dioxide", "nameRu": "Углекислый газ",
+    "mass": 44.01, "state": "gas", "color": "#aaaaaa",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": true, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Product of combustion and respiration. Denser than air — extinguishes fire.",
+    "descriptionRu": "Продукт горения и дыхания. Тяжелее воздуха — тушит огонь.",
+    "gameEffects": ["fire_extinguisher", "suffocant"]
+  },
+  {
+    "id": "CO", "formula": "CO", "name": "Carbon Monoxide", "nameRu": "Угарный газ",
+    "mass": 28.01, "state": "gas", "color": "#cccccc",
+    "properties": { "flammable": true, "toxic": true, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Odorless, deadly poison. Binds to hemoglobin 200x stronger than oxygen.",
+    "descriptionRu": "Без запаха, смертельно ядовит. Связывается с гемоглобином в 200 раз сильнее кислорода.",
+    "gameEffects": ["poison_gas", "fuel"]
+  },
+  {
+    "id": "HCl", "formula": "HCl", "name": "Hydrochloric Acid", "nameRu": "Соляная кислота",
+    "mass": 36.46, "state": "liquid", "color": "#ccff00",
+    "properties": { "flammable": false, "toxic": true, "explosive": false, "acidic": true, "basic": false, "oxidizer": false, "corrosive": true },
+    "description": "Strong acid. Dissolves metals and limestone. Present in stomach acid.",
+    "descriptionRu": "Сильная кислота. Растворяет металлы и известняк. Содержится в желудочном соке.",
+    "gameEffects": ["dissolve_metal", "dissolve_stone", "damage"]
+  },
+  {
+    "id": "NaOH", "formula": "NaOH", "name": "Sodium Hydroxide", "nameRu": "Гидроксид натрия",
+    "mass": 40.00, "state": "solid", "color": "#f5f5f5",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": true },
+    "description": "Lye. Extremely caustic. Used for soap making and as a powerful cleaning agent.",
+    "descriptionRu": "Щёлочь. Крайне едкий. Используется для мыловарения и как мощное чистящее средство.",
+    "gameEffects": ["soap_making", "corrosive_weapon", "cleaning"]
+  },
+  {
+    "id": "KOH", "formula": "KOH", "name": "Potassium Hydroxide", "nameRu": "Гидроксид калия",
+    "mass": 56.11, "state": "solid", "color": "#f0f0f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": true },
+    "description": "Caustic potash. Even stronger base than NaOH. Key in fertilizer production.",
+    "descriptionRu": "Едкое кали. Ещё более сильное основание, чем NaOH. Ключ к производству удобрений.",
+    "gameEffects": ["corrosive_weapon", "fertilizer_base"]
+  },
+  {
+    "id": "CaO", "formula": "CaO", "name": "Calcium Oxide", "nameRu": "Негашёная известь",
+    "mass": 56.08, "state": "solid", "color": "#f5f5dc",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": true },
+    "description": "Quickite. Reacts violently with water, generating intense heat. Building material.",
+    "descriptionRu": "Негашёная известь. Бурно реагирует с водой, выделяя сильное тепло. Строительный материал.",
+    "gameEffects": ["heat_source", "building", "disinfectant"]
+  },
+  {
+    "id": "CaOH2", "formula": "Ca(OH)₂", "name": "Calcium Hydroxide", "nameRu": "Гашёная известь",
+    "mass": 74.09, "state": "solid", "color": "#f5f5f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": false },
+    "description": "Slaked lime. Used in mortar, plaster, and water purification.",
+    "descriptionRu": "Гашёная известь. Используется в строительном растворе, штукатурке и очистке воды.",
+    "gameEffects": ["building_mortar", "water_purification", "disinfectant"]
+  },
+  {
+    "id": "MgO", "formula": "MgO", "name": "Magnesium Oxide", "nameRu": "Оксид магния",
+    "mass": 40.30, "state": "solid", "color": "#ffffff",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": false },
+    "description": "Produced by burning magnesium with a blinding white flash. Refractory material.",
+    "descriptionRu": "Образуется при горении магния с ослепительной белой вспышкой. Огнеупорный материал.",
+    "gameEffects": ["flash_blind", "refractory"]
+  },
+  {
+    "id": "Fe2O3", "formula": "Fe₂O₃", "name": "Iron(III) Oxide", "nameRu": "Оксид железа (ржавчина)",
+    "mass": 159.69, "state": "solid", "color": "#993300",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Rust. Indicator of aging metal. Key ingredient for thermite (with aluminum).",
+    "descriptionRu": "Ржавчина. Индикатор старения металла. Ключевой ингредиент термита (с алюминием).",
+    "gameEffects": ["thermite_ingredient", "pigment"]
+  },
+  {
+    "id": "SiO2", "formula": "SiO₂", "name": "Silicon Dioxide", "nameRu": "Диоксид кремния",
+    "mass": 60.08, "state": "solid", "color": "#e8e8e8",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Silica. Main component of sand, quartz, and glass. Extremely hard.",
+    "descriptionRu": "Кремнезём. Основной компонент песка, кварца и стекла. Крайне твёрдый.",
+    "gameEffects": ["glass_making", "abrasive", "building"]
+  },
+  {
+    "id": "FeS", "formula": "FeS", "name": "Iron Sulfide", "nameRu": "Сульфид железа",
+    "mass": 87.91, "state": "solid", "color": "#b8a000",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Fool's gold (pyrite). Sparks when struck — natural fire starter.",
+    "descriptionRu": "Пирит (золото дураков). Искрит при ударе — природное огниво.",
+    "gameEffects": ["fire_starter", "trade_decoy"]
+  },
+  {
+    "id": "ZnS", "formula": "ZnS", "name": "Zinc Sulfide", "nameRu": "Сульфид цинка",
+    "mass": 97.47, "state": "solid", "color": "#eeffdd",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Phosphorescent — glows in the dark after exposure to light. Natural night-light.",
+    "descriptionRu": "Фосфоресцирует — светится в темноте после облучения светом. Природный ночник.",
+    "gameEffects": ["glow", "cave_light", "marking"]
+  },
+  {
+    "id": "CuS", "formula": "CuS", "name": "Copper Sulfide", "nameRu": "Сульфид меди",
+    "mass": 95.61, "state": "solid", "color": "#1a1a2e",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Dark mineral. Copper ore found near volcanic activity.",
+    "descriptionRu": "Тёмный минерал. Медная руда, встречающаяся вблизи вулканической активности.",
+    "gameEffects": ["pigment", "copper_source"]
+  },
+  {
+    "id": "KCl", "formula": "KCl", "name": "Potassium Chloride", "nameRu": "Хлорид калия",
+    "mass": 74.55, "state": "solid", "color": "#f0f0f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Potash salt. Essential plant fertilizer. Salt substitute for food.",
+    "descriptionRu": "Калийная соль. Необходимое удобрение для растений. Заменитель соли в пище.",
+    "gameEffects": ["fertilizer", "preservation"]
+  },
+  {
+    "id": "SO2", "formula": "SO₂", "name": "Sulfur Dioxide", "nameRu": "Диоксид серы",
+    "mass": 64.07, "state": "gas", "color": "#cccc00",
+    "properties": { "flammable": false, "toxic": true, "explosive": false, "acidic": true, "basic": false, "oxidizer": false, "corrosive": true },
+    "description": "Pungent, suffocating gas. Fumigant and preservative. Causes acid rain.",
+    "descriptionRu": "Едкий, удушливый газ. Фумигант и консервант. Вызывает кислотные дожди.",
+    "gameEffects": ["fumigant", "area_denial", "preservation"]
+  },
+  {
+    "id": "CaCO3", "formula": "CaCO₃", "name": "Calcium Carbonate", "nameRu": "Карбонат кальция",
+    "mass": 100.09, "state": "solid", "color": "#f5f0e0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": false },
+    "description": "Limestone, chalk, marble. Building material. Neutralizes acid soil and acid attacks.",
+    "descriptionRu": "Известняк, мел, мрамор. Строительный материал. Нейтрализует кислую почву и кислотные атаки.",
+    "gameEffects": ["building", "acid_neutralizer", "soil_amendment"]
+  },
+  {
+    "id": "NaHCO3", "formula": "NaHCO₃", "name": "Sodium Bicarbonate", "nameRu": "Пищевая сода",
+    "mass": 84.01, "state": "solid", "color": "#ffffff",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": true, "oxidizer": false, "corrosive": false },
+    "description": "Baking soda. Neutralizes acids, extinguishes grease fires, gentle cleaning agent.",
+    "descriptionRu": "Пищевая сода. Нейтрализует кислоты, тушит жировые пожары, мягкое чистящее средство.",
+    "gameEffects": ["acid_neutralizer", "fire_extinguisher", "baking"]
+  },
+  {
+    "id": "KNO3", "formula": "KNO₃", "name": "Potassium Nitrate", "nameRu": "Калиевая селитра",
+    "mass": 101.10, "state": "solid", "color": "#f0f0f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": true, "corrosive": false },
+    "description": "Saltpeter. Powerful oxidizer. Key component of black gunpowder (with sulfur and charcoal).",
+    "descriptionRu": "Селитра. Мощный окислитель. Ключевой компонент чёрного пороха (с серой и углём).",
+    "gameEffects": ["gunpowder_ingredient", "oxidizer", "fertilizer"]
+  },
+  {
+    "id": "ZnO", "formula": "ZnO", "name": "Zinc Oxide", "nameRu": "Оксид цинка",
+    "mass": 81.38, "state": "solid", "color": "#ffffff",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "White powder. UV protection, wound healing, anti-inflammatory. Used in sunscreen and ointments.",
+    "descriptionRu": "Белый порошок. Защита от УФ, заживление ран, противовоспалительное. Основа мазей.",
+    "gameEffects": ["healing_salve", "sun_protection"]
+  },
+  {
+    "id": "Al2O3", "formula": "Al₂O₃", "name": "Aluminum Oxide", "nameRu": "Оксид алюминия",
+    "mass": 101.96, "state": "solid", "color": "#f0f0f0",
+    "properties": { "flammable": false, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Corundum. Extremely hard (9 on Mohs scale). Rubies and sapphires are colored alumina.",
+    "descriptionRu": "Корунд. Крайне твёрдый (9 по шкале Мооса). Рубины и сапфиры — окрашенный корунд.",
+    "gameEffects": ["abrasive", "armor_material", "gemstone"]
+  },
+  {
+    "id": "CH4", "formula": "CH₄", "name": "Methane", "nameRu": "Метан",
+    "mass": 16.04, "state": "gas", "color": "#aaddff",
+    "properties": { "flammable": true, "toxic": false, "explosive": true, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Simplest hydrocarbon. Odorless, highly flammable. Main component of natural gas.",
+    "descriptionRu": "Простейший углеводород. Без запаха, легковоспламеняем. Основной компонент природного газа.",
+    "gameEffects": ["fuel", "explosive_gas", "lantern_fuel"]
+  },
+  {
+    "id": "C2H5OH", "formula": "C₂H₅OH", "name": "Ethanol", "nameRu": "Этанол",
+    "mass": 46.07, "state": "liquid", "color": "#eeeeff",
+    "properties": { "flammable": true, "toxic": false, "explosive": false, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Drinking alcohol. Disinfectant, fuel, solvent. Intoxicates NPCs.",
+    "descriptionRu": "Питьевой спирт. Дезинфектант, топливо, растворитель. Опьяняет NPC.",
+    "gameEffects": ["disinfectant", "fuel", "intoxicant", "solvent"]
+  },
+  {
+    "id": "GUNPOWDER", "formula": "KNO₃+S+C", "name": "Black Gunpowder", "nameRu": "Чёрный порох",
+    "mass": 165.17, "state": "solid", "color": "#333333",
+    "properties": { "flammable": true, "toxic": false, "explosive": true, "acidic": false, "basic": false, "oxidizer": false, "corrosive": false },
+    "description": "Explosive mixture of saltpeter, sulfur, and charcoal. The discovery that changed civilizations.",
+    "descriptionRu": "Взрывчатая смесь селитры, серы и угля. Открытие, изменившее цивилизации.",
+    "gameEffects": ["explosive", "propellant", "signal_flare"]
+  }
+]
diff --git a/src/data/elements.json b/src/data/elements.json
new file mode 100644
index 0000000..b11ddd0
--- /dev/null
+++ b/src/data/elements.json
@@ -0,0 +1,262 @@
+[
+  {
+    "symbol": "H",
+    "name": "Hydrogen",
+    "nameRu": "Водород",
+    "atomicNumber": 1,
+    "atomicMass": 1.008,
+    "electronegativity": 2.20,
+    "category": "nonmetal",
+    "state": "gas",
+    "color": "#ffffff",
+    "description": "Lightest element. Highly flammable gas. The most abundant element in the universe.",
+    "descriptionRu": "Легчайший элемент. Легковоспламеняемый газ. Самый распространённый элемент во вселенной."
+  },
+  {
+    "symbol": "He",
+    "name": "Helium",
+    "nameRu": "Гелий",
+    "atomicNumber": 2,
+    "atomicMass": 4.003,
+    "electronegativity": 0,
+    "category": "noble-gas",
+    "state": "gas",
+    "color": "#d9ffff",
+    "description": "Noble gas. Completely inert — refuses to react with anything. Lighter than air.",
+    "descriptionRu": "Благородный газ. Абсолютно инертен — не реагирует ни с чем. Легче воздуха."
+  },
+  {
+    "symbol": "C",
+    "name": "Carbon",
+    "nameRu": "Углерод",
+    "atomicNumber": 6,
+    "atomicMass": 12.011,
+    "electronegativity": 2.55,
+    "category": "nonmetal",
+    "state": "solid",
+    "color": "#333333",
+    "description": "Basis of all organic chemistry. Forms more compounds than any other element. Burns in oxygen.",
+    "descriptionRu": "Основа всей органической химии. Образует больше соединений, чем любой другой элемент. Горит в кислороде."
+  },
+  {
+    "symbol": "N",
+    "name": "Nitrogen",
+    "nameRu": "Азот",
+    "atomicNumber": 7,
+    "atomicMass": 14.007,
+    "electronegativity": 3.04,
+    "category": "nonmetal",
+    "state": "gas",
+    "color": "#3050f8",
+    "description": "Makes up 78% of air. Very stable — triple bond is hard to break. Essential for life (proteins, DNA).",
+    "descriptionRu": "Составляет 78% воздуха. Очень стабилен — тройную связь трудно разорвать. Необходим для жизни (белки, ДНК)."
+  },
+  {
+    "symbol": "O",
+    "name": "Oxygen",
+    "nameRu": "Кислород",
+    "atomicNumber": 8,
+    "atomicMass": 15.999,
+    "electronegativity": 3.44,
+    "category": "nonmetal",
+    "state": "gas",
+    "color": "#ff0d0d",
+    "description": "Essential for combustion and respiration. Highly reactive oxidizer. 21% of air.",
+    "descriptionRu": "Необходим для горения и дыхания. Сильный окислитель. 21% воздуха."
+  },
+  {
+    "symbol": "Na",
+    "name": "Sodium",
+    "nameRu": "Натрий",
+    "atomicNumber": 11,
+    "atomicMass": 22.990,
+    "electronegativity": 0.93,
+    "category": "alkali-metal",
+    "state": "solid",
+    "color": "#c8c8c8",
+    "description": "Soft alkali metal. Reacts violently with water — explosion and flame! Store away from moisture.",
+    "descriptionRu": "Мягкий щелочной металл. Бурно реагирует с водой — взрыв и пламя! Хранить вдали от влаги."
+  },
+  {
+    "symbol": "Mg",
+    "name": "Magnesium",
+    "nameRu": "Магний",
+    "atomicNumber": 12,
+    "atomicMass": 24.305,
+    "electronegativity": 1.31,
+    "category": "alkaline-earth",
+    "state": "solid",
+    "color": "#8aff00",
+    "description": "Burns with an intensely bright white flame. Used in flares and incendiary devices.",
+    "descriptionRu": "Горит ослепительно ярким белым пламенем. Используется в сигнальных ракетах и зажигательных устройствах."
+  },
+  {
+    "symbol": "Al",
+    "name": "Aluminum",
+    "nameRu": "Алюминий",
+    "atomicNumber": 13,
+    "atomicMass": 26.982,
+    "electronegativity": 1.61,
+    "category": "post-transition-metal",
+    "state": "solid",
+    "color": "#bfa6a6",
+    "description": "Light, strong metal. Oxide layer protects from corrosion. Key ingredient in thermite.",
+    "descriptionRu": "Лёгкий, прочный металл. Оксидная плёнка защищает от коррозии. Ключевой ингредиент термита."
+  },
+  {
+    "symbol": "Si",
+    "name": "Silicon",
+    "nameRu": "Кремний",
+    "atomicNumber": 14,
+    "atomicMass": 28.086,
+    "electronegativity": 1.90,
+    "category": "metalloid",
+    "state": "solid",
+    "color": "#f0c8a0",
+    "description": "Semiconductor. Basis of glass, ceramics, and electronics. Second most abundant in Earth's crust.",
+    "descriptionRu": "Полупроводник. Основа стекла, керамики и электроники. Второй по распространённости в земной коре."
+  },
+  {
+    "symbol": "P",
+    "name": "Phosphorus",
+    "nameRu": "Фосфор",
+    "atomicNumber": 15,
+    "atomicMass": 30.974,
+    "electronegativity": 2.19,
+    "category": "nonmetal",
+    "state": "solid",
+    "color": "#ff8000",
+    "description": "White phosphorus glows in the dark and ignites spontaneously. Essential for ATP (biological energy).",
+    "descriptionRu": "Белый фосфор светится в темноте и самовоспламеняется. Необходим для АТФ (биологическая энергия)."
+  },
+  {
+    "symbol": "S",
+    "name": "Sulfur",
+    "nameRu": "Сера",
+    "atomicNumber": 16,
+    "atomicMass": 32.065,
+    "electronegativity": 2.58,
+    "category": "nonmetal",
+    "state": "solid",
+    "color": "#ffff30",
+    "description": "Yellow solid with a distinctive smell. Burns with blue flame. Component of gunpowder.",
+    "descriptionRu": "Жёлтое твёрдое вещество с характерным запахом. Горит синим пламенем. Компонент пороха."
+  },
+  {
+    "symbol": "Cl",
+    "name": "Chlorine",
+    "nameRu": "Хлор",
+    "atomicNumber": 17,
+    "atomicMass": 35.453,
+    "electronegativity": 3.16,
+    "category": "halogen",
+    "state": "gas",
+    "color": "#1ff01f",
+    "description": "Toxic yellow-green gas. Powerful disinfectant. Combines readily with metals to form salts.",
+    "descriptionRu": "Ядовитый жёлто-зелёный газ. Мощный дезинфектант. Легко соединяется с металлами, образуя соли."
+  },
+  {
+    "symbol": "K",
+    "name": "Potassium",
+    "nameRu": "Калий",
+    "atomicNumber": 19,
+    "atomicMass": 39.098,
+    "electronegativity": 0.82,
+    "category": "alkali-metal",
+    "state": "solid",
+    "color": "#8f40d4",
+    "description": "Even more reactive than sodium with water — violent purple-flame explosion. Essential nutrient for plants.",
+    "descriptionRu": "Ещё активнее натрия при контакте с водой — бурный взрыв с фиолетовым пламенем. Необходим растениям."
+  },
+  {
+    "symbol": "Ca",
+    "name": "Calcium",
+    "nameRu": "Кальций",
+    "atomicNumber": 20,
+    "atomicMass": 40.078,
+    "electronegativity": 1.00,
+    "category": "alkaline-earth",
+    "state": "solid",
+    "color": "#e0e0e0",
+    "description": "Essential for bones and shells. Reacts with water, but less violently than sodium. Component of limestone and cement.",
+    "descriptionRu": "Необходим для костей и раковин. Реагирует с водой, но менее бурно, чем натрий. Компонент известняка и цемента."
+  },
+  {
+    "symbol": "Fe",
+    "name": "Iron",
+    "nameRu": "Железо",
+    "atomicNumber": 26,
+    "atomicMass": 55.845,
+    "electronegativity": 1.83,
+    "category": "transition-metal",
+    "state": "solid",
+    "color": "#a0a0a0",
+    "description": "Strong, abundant metal. Rusts in moist air. Core of Earth is mostly iron. Magnetic.",
+    "descriptionRu": "Прочный, распространённый металл. Ржавеет на влажном воздухе. Ядро Земли в основном из железа. Магнитен."
+  },
+  {
+    "symbol": "Cu",
+    "name": "Copper",
+    "nameRu": "Медь",
+    "atomicNumber": 29,
+    "atomicMass": 63.546,
+    "electronegativity": 1.90,
+    "category": "transition-metal",
+    "state": "solid",
+    "color": "#c88033",
+    "description": "Excellent conductor of electricity and heat. Turns green (patina) over time. Antibacterial properties.",
+    "descriptionRu": "Отличный проводник электричества и тепла. Зеленеет (патина) со временем. Антибактериальные свойства."
+  },
+  {
+    "symbol": "Zn",
+    "name": "Zinc",
+    "nameRu": "Цинк",
+    "atomicNumber": 30,
+    "atomicMass": 65.38,
+    "electronegativity": 1.65,
+    "category": "transition-metal",
+    "state": "solid",
+    "color": "#7d80b0",
+    "description": "Protects iron from rusting (galvanization). Zinc sulfide glows under UV light. Essential trace nutrient.",
+    "descriptionRu": "Защищает железо от ржавчины (гальванизация). Сульфид цинка светится в УФ-свете. Необходимый микроэлемент."
+  },
+  {
+    "symbol": "Sn",
+    "name": "Tin",
+    "nameRu": "Олово",
+    "atomicNumber": 50,
+    "atomicMass": 118.71,
+    "electronegativity": 1.96,
+    "category": "post-transition-metal",
+    "state": "solid",
+    "color": "#668080",
+    "description": "Soft, malleable metal. Resists corrosion. Used for solder and tin plating. Alloy with copper makes bronze.",
+    "descriptionRu": "Мягкий, ковкий металл. Устойчив к коррозии. Используется для пайки и лужения. Сплав с медью — бронза."
+  },
+  {
+    "symbol": "Au",
+    "name": "Gold",
+    "nameRu": "Золото",
+    "atomicNumber": 79,
+    "atomicMass": 196.967,
+    "electronegativity": 2.54,
+    "category": "transition-metal",
+    "state": "solid",
+    "color": "#ffd123",
+    "description": "Extremely unreactive noble metal. Does not corrode or tarnish. Excellent conductor. Very rare.",
+    "descriptionRu": "Крайне инертный благородный металл. Не корродирует и не тускнеет. Отличный проводник. Очень редок."
+  },
+  {
+    "symbol": "Hg",
+    "name": "Mercury",
+    "nameRu": "Ртуть",
+    "atomicNumber": 80,
+    "atomicMass": 200.592,
+    "electronegativity": 2.00,
+    "category": "transition-metal",
+    "state": "liquid",
+    "color": "#b8b8d0",
+    "description": "Only metal that is liquid at room temperature. Extremely toxic — damages brain and kidneys. Handle with extreme care.",
+    "descriptionRu": "Единственный металл, жидкий при комнатной температуре. Крайне токсичен — поражает мозг и почки. Обращаться с предельной осторожностью."
+  }
+]
diff --git a/src/data/reactions.json b/src/data/reactions.json
new file mode 100644
index 0000000..79eaa0b
--- /dev/null
+++ b/src/data/reactions.json
@@ -0,0 +1,326 @@
+[
+  {
+    "id": "synth_nacl", "type": "synthesis",
+    "reactants": [{ "id": "Na", "count": 1 }, { "id": "Cl", "count": 1 }],
+    "products": [{ "id": "NaCl", "count": 1 }],
+    "energyChange": -40,
+    "description": "Sodium and chlorine combine in a vigorous exothermic reaction to form table salt.",
+    "descriptionRu": "Натрий и хлор соединяются в бурной экзотермической реакции, образуя поваренную соль.",
+    "difficulty": 1
+  },
+  {
+    "id": "synth_kcl", "type": "synthesis",
+    "reactants": [{ "id": "K", "count": 1 }, { "id": "Cl", "count": 1 }],
+    "products": [{ "id": "KCl", "count": 1 }],
+    "energyChange": -44,
+    "description": "Potassium bonds with chlorine to form potassium chloride — a valuable fertilizer salt.",
+    "descriptionRu": "Калий связывается с хлором, образуя хлорид калия — ценную удобрительную соль.",
+    "difficulty": 1
+  },
+  {
+    "id": "synth_fes", "type": "synthesis",
+    "reactants": [{ "id": "Fe", "count": 1 }, { "id": "S", "count": 1 }],
+    "products": [{ "id": "FeS", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -10,
+    "description": "Iron and sulfur combine when heated to form iron sulfide (pyrite) — fool's gold that sparks when struck.",
+    "descriptionRu": "Железо и сера при нагревании образуют сульфид железа (пирит) — золото дураков, искрящее при ударе.",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_cus", "type": "synthesis",
+    "reactants": [{ "id": "Cu", "count": 1 }, { "id": "S", "count": 1 }],
+    "products": [{ "id": "CuS", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -5,
+    "description": "Copper reacts with sulfur when heated, forming dark copper sulfide.",
+    "descriptionRu": "Медь реагирует с серой при нагревании, образуя тёмный сульфид меди.",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_zns", "type": "synthesis",
+    "reactants": [{ "id": "Zn", "count": 1 }, { "id": "S", "count": 1 }],
+    "products": [{ "id": "ZnS", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -20,
+    "description": "Zinc and sulfur combine exothermically to form zinc sulfide — a phosphorescent compound that glows in the dark.",
+    "descriptionRu": "Цинк и сера экзотермически образуют сульфид цинка — фосфоресцирующее соединение, светящееся в темноте.",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_h2o", "type": "synthesis",
+    "reactants": [{ "id": "H", "count": 2 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "H2O", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -70,
+    "description": "Hydrogen combustion. Two parts hydrogen + one part oxygen ignite to produce water, releasing tremendous energy.",
+    "descriptionRu": "Горение водорода. Два объёма водорода + один объём кислорода воспламеняются, образуя воду и выделяя огромную энергию.",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_hcl", "type": "synthesis",
+    "reactants": [{ "id": "H", "count": 1 }, { "id": "Cl", "count": 1 }],
+    "products": [{ "id": "HCl", "count": 1 }],
+    "energyChange": -9,
+    "description": "Hydrogen and chlorine combine to form hydrochloric acid — a strong acid that dissolves metals.",
+    "descriptionRu": "Водород и хлор образуют соляную кислоту — сильную кислоту, растворяющую металлы.",
+    "difficulty": 1
+  },
+  {
+    "id": "comb_co2", "type": "combustion",
+    "reactants": [{ "id": "C", "count": 1 }, { "id": "O", "count": 2 }],
+    "products": [{ "id": "CO2", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -40,
+    "description": "Carbon burns in excess oxygen to produce carbon dioxide. Complete combustion.",
+    "descriptionRu": "Углерод горит в избытке кислорода, образуя углекислый газ. Полное сгорание.",
+    "difficulty": 1
+  },
+  {
+    "id": "comb_co", "type": "combustion",
+    "reactants": [{ "id": "C", "count": 1 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "CO", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -11,
+    "description": "Carbon burns in limited oxygen → deadly carbon monoxide. Odorless killer.",
+    "descriptionRu": "Углерод горит при недостатке кислорода → смертельный угарный газ. Убийца без запаха.",
+    "difficulty": 2
+  },
+  {
+    "id": "comb_so2", "type": "combustion",
+    "reactants": [{ "id": "S", "count": 1 }, { "id": "O", "count": 2 }],
+    "products": [{ "id": "SO2", "count": 1 }],
+    "conditions": { "minTemp": 300 },
+    "energyChange": -30,
+    "description": "Sulfur burns with a blue flame, producing choking sulfur dioxide gas.",
+    "descriptionRu": "Сера горит синим пламенем, выделяя удушливый сернистый газ.",
+    "difficulty": 1
+  },
+  {
+    "id": "comb_mgo", "type": "combustion",
+    "reactants": [{ "id": "Mg", "count": 1 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "MgO", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -60,
+    "description": "Magnesium burns with an intensely bright white flame — blinding! Produces white magnesium oxide ash.",
+    "descriptionRu": "Магний горит ослепительно ярким белым пламенем! Образует белый пепел оксида магния.",
+    "difficulty": 1
+  },
+  {
+    "id": "comb_fe2o3", "type": "combustion",
+    "reactants": [{ "id": "Fe", "count": 2 }, { "id": "O", "count": 3 }],
+    "products": [{ "id": "Fe2O3", "count": 1 }],
+    "conditions": { "minTemp": 1000 },
+    "energyChange": -25,
+    "description": "Iron oxidation. At furnace temperatures, iron combines with oxygen to form iron oxide (rust).",
+    "descriptionRu": "Окисление железа. При температуре печи железо соединяется с кислородом, образуя оксид железа (ржавчину).",
+    "difficulty": 3
+  },
+  {
+    "id": "comb_cao", "type": "combustion",
+    "reactants": [{ "id": "Ca", "count": 1 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "CaO", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -63,
+    "description": "Calcium burns in oxygen to form quicklime — a powerful desiccant and heat source when mixed with water.",
+    "descriptionRu": "Кальций горит в кислороде, образуя негашёную известь — мощный осушитель и источник тепла при смешении с водой.",
+    "difficulty": 2
+  },
+  {
+    "id": "comb_zno", "type": "combustion",
+    "reactants": [{ "id": "Zn", "count": 1 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "ZnO", "count": 1 }],
+    "conditions": { "minTemp": 500 },
+    "energyChange": -35,
+    "description": "Zinc burns with a blue-green flame, producing zinc oxide — a healing white powder.",
+    "descriptionRu": "Цинк горит сине-зелёным пламенем, образуя оксид цинка — целебный белый порошок.",
+    "difficulty": 2
+  },
+  {
+    "id": "comb_sio2", "type": "combustion",
+    "reactants": [{ "id": "Si", "count": 1 }, { "id": "O", "count": 2 }],
+    "products": [{ "id": "SiO2", "count": 1 }],
+    "conditions": { "minTemp": 1000 },
+    "energyChange": -90,
+    "description": "Silicon combines with oxygen at extreme heat to form silica (quartz) — the basis of glass.",
+    "descriptionRu": "Кремний соединяется с кислородом при экстремальном нагреве, образуя кремнезём (кварц) — основу стекла.",
+    "difficulty": 4
+  },
+  {
+    "id": "comb_al2o3", "type": "combustion",
+    "reactants": [{ "id": "Al", "count": 2 }, { "id": "O", "count": 3 }],
+    "products": [{ "id": "Al2O3", "count": 1 }],
+    "conditions": { "minTemp": 1000 },
+    "energyChange": -84,
+    "description": "Aluminum combustion produces alumina (corundum) — nearly as hard as diamond.",
+    "descriptionRu": "Горение алюминия производит корунд — почти такой же твёрдый, как алмаз.",
+    "difficulty": 4
+  },
+  {
+    "id": "synth_ch4", "type": "synthesis",
+    "reactants": [{ "id": "C", "count": 1 }, { "id": "H", "count": 4 }],
+    "products": [{ "id": "CH4", "count": 1 }],
+    "conditions": { "minTemp": 500, "catalyst": "Fe" },
+    "energyChange": -8,
+    "description": "Carbon + hydrogen with iron catalyst → methane. Simplest hydrocarbon fuel.",
+    "descriptionRu": "Углерод + водород с железным катализатором → метан. Простейшее углеводородное топливо.",
+    "difficulty": 3
+  },
+  {
+    "id": "synth_naoh", "type": "synthesis",
+    "reactants": [{ "id": "Na", "count": 1 }, { "id": "O", "count": 1 }, { "id": "H", "count": 1 }],
+    "products": [{ "id": "NaOH", "count": 1 }],
+    "energyChange": -45,
+    "description": "Direct synthesis of sodium hydroxide (lye). Extremely caustic — handle carefully!",
+    "descriptionRu": "Прямой синтез гидроксида натрия (щёлочи). Крайне едкий — обращаться осторожно!",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_koh", "type": "synthesis",
+    "reactants": [{ "id": "K", "count": 1 }, { "id": "O", "count": 1 }, { "id": "H", "count": 1 }],
+    "products": [{ "id": "KOH", "count": 1 }],
+    "energyChange": -49,
+    "description": "Direct synthesis of potassium hydroxide. Even more reactive than NaOH.",
+    "descriptionRu": "Прямой синтез гидроксида калия. Ещё активнее, чем NaOH.",
+    "difficulty": 2
+  },
+  {
+    "id": "synth_caco3", "type": "synthesis",
+    "reactants": [{ "id": "Ca", "count": 1 }, { "id": "C", "count": 1 }, { "id": "O", "count": 3 }],
+    "products": [{ "id": "CaCO3", "count": 1 }],
+    "energyChange": -12,
+    "description": "Calcium, carbon, and oxygen form calcium carbonate — the building block of limestone and shells.",
+    "descriptionRu": "Кальций, углерод и кислород образуют карбонат кальция — строительный блок известняка и ракушек.",
+    "difficulty": 3
+  },
+  {
+    "id": "synth_nahco3", "type": "synthesis",
+    "reactants": [{ "id": "Na", "count": 1 }, { "id": "H", "count": 1 }, { "id": "C", "count": 1 }, { "id": "O", "count": 3 }],
+    "products": [{ "id": "NaHCO3", "count": 1 }],
+    "energyChange": -10,
+    "description": "Synthesis of sodium bicarbonate (baking soda). Versatile acid neutralizer.",
+    "descriptionRu": "Синтез гидрокарбоната натрия (пищевая сода). Универсальный нейтрализатор кислот.",
+    "difficulty": 3
+  },
+  {
+    "id": "synth_kno3", "type": "synthesis",
+    "reactants": [{ "id": "K", "count": 1 }, { "id": "N", "count": 1 }, { "id": "O", "count": 3 }],
+    "products": [{ "id": "KNO3", "count": 1 }],
+    "energyChange": -5,
+    "description": "Potassium nitrate (saltpeter). A powerful oxidizer — one third of gunpowder.",
+    "descriptionRu": "Нитрат калия (селитра). Мощный окислитель — треть состава пороха.",
+    "difficulty": 3
+  },
+  {
+    "id": "synth_caoh2", "type": "synthesis",
+    "reactants": [{ "id": "Ca", "count": 1 }, { "id": "O", "count": 2 }, { "id": "H", "count": 2 }],
+    "products": [{ "id": "CaOH2", "count": 1 }],
+    "energyChange": -15,
+    "description": "Calcium hydroxide (slaked lime). Essential for mortar and water purification.",
+    "descriptionRu": "Гидроксид кальция (гашёная известь). Необходим для строительного раствора и очистки воды.",
+    "difficulty": 3
+  },
+  {
+    "id": "repl_na_h2o", "type": "single-replacement",
+    "reactants": [{ "id": "Na", "count": 1 }, { "id": "H2O", "count": 1 }],
+    "products": [{ "id": "NaOH", "count": 1 }, { "id": "H", "count": 1 }],
+    "energyChange": -80,
+    "description": "VIOLENT! Sodium reacts explosively with water → lye + hydrogen gas + fire. Never drop sodium in water!",
+    "descriptionRu": "ОПАСНО! Натрий взрывоподобно реагирует с водой → щёлочь + водород + пламя. Никогда не бросайте натрий в воду!",
+    "difficulty": 1
+  },
+  {
+    "id": "repl_k_h2o", "type": "single-replacement",
+    "reactants": [{ "id": "K", "count": 1 }, { "id": "H2O", "count": 1 }],
+    "products": [{ "id": "KOH", "count": 1 }, { "id": "H", "count": 1 }],
+    "energyChange": -95,
+    "description": "EXPLOSIVE! Potassium reacts even more violently than sodium with water — purple flame, detonation!",
+    "descriptionRu": "ВЗРЫВ! Калий реагирует с водой ещё бурнее натрия — фиолетовое пламя, детонация!",
+    "difficulty": 1
+  },
+  {
+    "id": "repl_cao_h2o", "type": "single-replacement",
+    "reactants": [{ "id": "CaO", "count": 1 }, { "id": "H2O", "count": 1 }],
+    "products": [{ "id": "CaOH2", "count": 1 }],
+    "energyChange": -65,
+    "description": "Quicklime + water → slaked lime + intense heat. Can boil water! Used in ancient warfare.",
+    "descriptionRu": "Негашёная известь + вода → гашёная известь + сильный нагрев. Может вскипятить воду! Использовалось в древних войнах.",
+    "difficulty": 1
+  },
+  {
+    "id": "ab_naoh_hcl", "type": "acid-base",
+    "reactants": [{ "id": "NaOH", "count": 1 }, { "id": "HCl", "count": 1 }],
+    "products": [{ "id": "NaCl", "count": 1 }, { "id": "H2O", "count": 1 }],
+    "energyChange": -57,
+    "description": "Classic neutralization: acid + base → salt + water. NaOH + HCl → NaCl + H₂O.",
+    "descriptionRu": "Классическая нейтрализация: кислота + основание → соль + вода. NaOH + HCl → NaCl + H₂O.",
+    "difficulty": 2
+  },
+  {
+    "id": "ab_koh_hcl", "type": "acid-base",
+    "reactants": [{ "id": "KOH", "count": 1 }, { "id": "HCl", "count": 1 }],
+    "products": [{ "id": "KCl", "count": 1 }, { "id": "H2O", "count": 1 }],
+    "energyChange": -57,
+    "description": "Neutralization: potassium hydroxide + hydrochloric acid → potassium chloride + water.",
+    "descriptionRu": "Нейтрализация: гидроксид калия + соляная кислота → хлорид калия + вода.",
+    "difficulty": 2
+  },
+  {
+    "id": "ab_nahco3_hcl", "type": "acid-base",
+    "reactants": [{ "id": "NaHCO3", "count": 1 }, { "id": "HCl", "count": 1 }],
+    "products": [{ "id": "NaCl", "count": 1 }, { "id": "H2O", "count": 1 }, { "id": "CO2", "count": 1 }],
+    "energyChange": -12,
+    "description": "Baking soda fizzes violently with acid! Produces salt, water, and carbon dioxide gas. Classic volcano reaction.",
+    "descriptionRu": "Сода бурно шипит при контакте с кислотой! Образуется соль, вода и углекислый газ. Классическая реакция «вулкан».",
+    "difficulty": 1
+  },
+  {
+    "id": "synth_gunpowder", "type": "synthesis",
+    "reactants": [{ "id": "KNO3", "count": 1 }, { "id": "S", "count": 1 }, { "id": "C", "count": 1 }],
+    "products": [{ "id": "GUNPOWDER", "count": 1 }],
+    "energyChange": 0,
+    "description": "The legendary mixture: saltpeter + sulfur + charcoal = black gunpowder. Handle with extreme care.",
+    "descriptionRu": "Легендарная смесь: селитра + сера + уголь = чёрный порох. Обращаться с предельной осторожностью.",
+    "difficulty": 4
+  },
+  {
+    "id": "redox_thermite", "type": "redox",
+    "reactants": [{ "id": "Fe2O3", "count": 1 }, { "id": "Al", "count": 2 }],
+    "products": [{ "id": "Fe", "count": 2 }, { "id": "Al2O3", "count": 1 }],
+    "conditions": { "minTemp": 1000 },
+    "energyChange": -100,
+    "description": "THERMITE! Iron oxide + aluminum → molten iron + alumina. Temperature exceeds 2500°C. Melts through anything.",
+    "descriptionRu": "ТЕРМИТ! Оксид железа + алюминий → расплавленное железо + корунд. Температура превышает 2500°C. Прожигает всё.",
+    "difficulty": 5
+  },
+  {
+    "id": "synth_ethanol", "type": "synthesis",
+    "reactants": [{ "id": "C", "count": 2 }, { "id": "H", "count": 6 }, { "id": "O", "count": 1 }],
+    "products": [{ "id": "C2H5OH", "count": 1 }],
+    "conditions": { "catalyst": "Cu" },
+    "energyChange": -3,
+    "description": "Ethanol synthesis requires a copper catalyst. The original chemistry of civilization — fermentation.",
+    "descriptionRu": "Синтез этанола требует медного катализатора. Изначальная химия цивилизации — ферментация.",
+    "difficulty": 4
+  },
+  {
+    "id": "decomp_h2o", "type": "decomposition",
+    "reactants": [{ "id": "H2O", "count": 1 }],
+    "products": [{ "id": "H", "count": 2 }, { "id": "O", "count": 1 }],
+    "conditions": { "requiresEnergy": true },
+    "energyChange": 70,
+    "description": "Electrolysis: electric current splits water into hydrogen and oxygen. Endothermic — needs energy input.",
+    "descriptionRu": "Электролиз: электрический ток разлагает воду на водород и кислород. Эндотермическая — требует энергии.",
+    "difficulty": 3
+  },
+  {
+    "id": "decomp_caco3", "type": "decomposition",
+    "reactants": [{ "id": "CaCO3", "count": 1 }],
+    "products": [{ "id": "CaO", "count": 1 }, { "id": "CO2", "count": 1 }],
+    "conditions": { "minTemp": 1000 },
+    "energyChange": 18,
+    "description": "Lime burning: heating limestone drives off CO₂, leaving quicklime. Ancient building technology.",
+    "descriptionRu": "Обжиг извести: нагрев известняка выгоняет CO₂, оставляя негашёную известь. Древняя строительная технология.",
+    "difficulty": 3
+  }
+]
diff --git a/tests/chemistry.test.ts b/tests/chemistry.test.ts
new file mode 100644
index 0000000..e9f6066
--- /dev/null
+++ b/tests/chemistry.test.ts
@@ -0,0 +1,347 @@
+import { describe, it, expect } from 'vitest';
+import { ElementRegistry } from '../src/chemistry/elements';
+import { CompoundRegistry } from '../src/chemistry/compounds';
+import { ReactionEngine } from '../src/chemistry/engine';
+
+// =============================================================================
+// ELEMENT REGISTRY
+// =============================================================================
+
+describe('ElementRegistry', () => {
+  it('should load all 20 elements', () => {
+    expect(ElementRegistry.count()).toBe(20);
+  });
+
+  it('should look up elements by symbol', () => {
+    const na = ElementRegistry.getBySymbol('Na');
+    expect(na).toBeDefined();
+    expect(na!.name).toBe('Sodium');
+    expect(na!.nameRu).toBe('Натрий');
+    expect(na!.atomicNumber).toBe(11);
+    expect(na!.atomicMass).toBeCloseTo(22.990, 2);
+    expect(na!.category).toBe('alkali-metal');
+  });
+
+  it('should look up elements by atomic number', () => {
+    const fe = ElementRegistry.getByNumber(26);
+    expect(fe).toBeDefined();
+    expect(fe!.symbol).toBe('Fe');
+    expect(fe!.name).toBe('Iron');
+  });
+
+  it('should return undefined for non-existent elements', () => {
+    expect(ElementRegistry.getBySymbol('Xx')).toBeUndefined();
+    expect(ElementRegistry.getByNumber(999)).toBeUndefined();
+  });
+
+  it('should have correct data for all elements (real periodic table)', () => {
+    const h = ElementRegistry.getBySymbol('H')!;
+    expect(h.atomicNumber).toBe(1);
+    expect(h.atomicMass).toBeCloseTo(1.008, 2);
+    expect(h.state).toBe('gas');
+
+    const hg = ElementRegistry.getBySymbol('Hg')!;
+    expect(hg.atomicNumber).toBe(80);
+    expect(hg.state).toBe('liquid'); // Only metal liquid at room temp!
+
+    const he = ElementRegistry.getBySymbol('He')!;
+    expect(he.category).toBe('noble-gas');
+    expect(he.electronegativity).toBe(0);
+
+    const au = ElementRegistry.getBySymbol('Au')!;
+    expect(au.atomicNumber).toBe(79);
+    expect(au.category).toBe('transition-metal');
+  });
+
+  it('should identify elements correctly', () => {
+    expect(ElementRegistry.isElement('Na')).toBe(true);
+    expect(ElementRegistry.isElement('Fe')).toBe(true);
+    expect(ElementRegistry.isElement('NaCl')).toBe(false);
+    expect(ElementRegistry.isElement('H2O')).toBe(false);
+  });
+});
+
+// =============================================================================
+// COMPOUND REGISTRY
+// =============================================================================
+
+describe('CompoundRegistry', () => {
+  it('should load all compounds', () => {
+    expect(CompoundRegistry.count()).toBeGreaterThanOrEqual(20);
+  });
+
+  it('should look up compounds by id', () => {
+    const water = CompoundRegistry.getById('H2O');
+    expect(water).toBeDefined();
+    expect(water!.name).toBe('Water');
+    expect(water!.formula).toBe('H₂O');
+    expect(water!.mass).toBeCloseTo(18.015, 2);
+    expect(water!.state).toBe('liquid');
+  });
+
+  it('should have game effects for each compound', () => {
+    const salt = CompoundRegistry.getById('NaCl')!;
+    expect(salt.gameEffects).toContain('preservation');
+
+    const gunpowder = CompoundRegistry.getById('GUNPOWDER')!;
+    expect(gunpowder.gameEffects).toContain('explosive');
+    expect(gunpowder.properties.explosive).toBe(true);
+  });
+
+  it('should correctly flag dangerous compounds', () => {
+    const hcl = CompoundRegistry.getById('HCl')!;
+    expect(hcl.properties.acidic).toBe(true);
+    expect(hcl.properties.corrosive).toBe(true);
+
+    const co = CompoundRegistry.getById('CO')!;
+    expect(co.properties.toxic).toBe(true);
+
+    const naoh = CompoundRegistry.getById('NaOH')!;
+    expect(naoh.properties.basic).toBe(true);
+    expect(naoh.properties.corrosive).toBe(true);
+  });
+
+  it('should identify compounds correctly', () => {
+    expect(CompoundRegistry.isCompound('NaCl')).toBe(true);
+    expect(CompoundRegistry.isCompound('H2O')).toBe(true);
+    expect(CompoundRegistry.isCompound('Na')).toBe(false);
+  });
+});
+
+// =============================================================================
+// REACTION ENGINE — SUCCESSFUL REACTIONS
+// =============================================================================
+
+describe('ReactionEngine — success', () => {
+  it('should produce NaCl from Na + Cl', () => {
+    const result = ReactionEngine.react([
+      { id: 'Na', count: 1 },
+      { id: 'Cl', count: 1 },
+    ]);
+    expect(result.success).toBe(true);
+    expect(result.products).toEqual([{ id: 'NaCl', count: 1 }]);
+  });
+
+  it('should produce H2O from 2H + O', () => {
+    const result = ReactionEngine.react(
+      [
+        { id: 'H', count: 2 },
+        { id: 'O', count: 1 },
+      ],
+      { minTemp: 500 },
+    );
+    expect(result.success).toBe(true);
+    expect(result.products).toEqual([{ id: 'H2O', count: 1 }]);
+  });
+
+  it('should produce CO2 from C + 2O with heat', () => {
+    const result = ReactionEngine.react(
+      [
+        { id: 'C', count: 1 },
+        { id: 'O', count: 2 },
+      ],
+      { minTemp: 500 },
+    );
+    expect(result.success).toBe(true);
+    expect(result.products).toEqual([{ id: 'CO2', count: 1 }]);
+    expect(result.reaction!.type).toBe('combustion');
+  });
+
+  it('should produce NaOH + H from Na + H2O (violent reaction)', () => {
+    const result = ReactionEngine.react([
+      { id: 'Na', count: 1 },
+      { id: 'H2O', count: 1 },
+    ]);
+    expect(result.success).toBe(true);
+    expect(result.products).toContainEqual({ id: 'NaOH', count: 1 });
+    expect(result.products).toContainEqual({ id: 'H', count: 1 });
+    expect(result.reaction!.energyChange).toBeLessThan(-50); // Very exothermic
+  });
+
+  it('should produce gunpowder from KNO3 + S + C', () => {
+    const result = ReactionEngine.react([
+      { id: 'KNO3', count: 1 },
+      { id: 'S', count: 1 },
+      { id: 'C', count: 1 },
+    ]);
+    expect(result.success).toBe(true);
+    expect(result.products).toEqual([{ id: 'GUNPOWDER', count: 1 }]);
+  });
+
+  it('should produce thermite: Fe2O3 + 2Al → 2Fe + Al2O3', () => {
+    const result = ReactionEngine.react(
+      [
+        { id: 'Fe2O3', count: 1 },
+        { id: 'Al', count: 2 },
+      ],
+      { minTemp: 1000 },
+    );
+    expect(result.success).toBe(true);
+    expect(result.products).toContainEqual({ id: 'Fe', count: 2 });
+    expect(result.products).toContainEqual({ id: 'Al2O3', count: 1 });
+    expect(result.reaction!.energyChange).toBe(-100); // Maximum exothermic
+  });
+
+  it('should produce NaCl + H2O from NaOH + HCl (neutralization)', () => {
+    const result = ReactionEngine.react([
+      { id: 'NaOH', count: 1 },
+      { id: 'HCl', count: 1 },
+    ]);
+    expect(result.success).toBe(true);
+    expect(result.products).toContainEqual({ id: 'NaCl', count: 1 });
+    expect(result.products).toContainEqual({ id: 'H2O', count: 1 });
+    expect(result.reaction!.type).toBe('acid-base');
+  });
+
+  it('should decompose H2O with energy input (electrolysis)', () => {
+    const result = ReactionEngine.react(
+      [{ id: 'H2O', count: 1 }],
+      { requiresEnergy: true },
+    );
+    expect(result.success).toBe(true);
+    expect(result.products).toContainEqual({ id: 'H', count: 2 });
+    expect(result.products).toContainEqual({ id: 'O', count: 1 });
+    expect(result.reaction!.energyChange).toBeGreaterThan(0); // Endothermic
+  });
+
+  it('reactant order should not matter (key is sorted)', () => {
+    const r1 = ReactionEngine.react([
+      { id: 'Cl', count: 1 },
+      { id: 'Na', count: 1 },
+    ]);
+    const r2 = ReactionEngine.react([
+      { id: 'Na', count: 1 },
+      { id: 'Cl', count: 1 },
+    ]);
+    expect(r1.success).toBe(true);
+    expect(r2.success).toBe(true);
+    expect(r1.products).toEqual(r2.products);
+  });
+});
+
+// =============================================================================
+// REACTION ENGINE — FAILURES (educational)
+// =============================================================================
+
+describe('ReactionEngine — failures', () => {
+  it('should reject noble gas reactions with explanation', () => {
+    const result = ReactionEngine.react([
+      { id: 'He', count: 1 },
+      { id: 'O', count: 1 },
+    ]);
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('noble gas');
+    expect(result.failureReasonRu).toContain('благородный газ');
+  });
+
+  it('should reject gold reactions with explanation', () => {
+    const result = ReactionEngine.react([
+      { id: 'Au', count: 1 },
+      { id: 'O', count: 1 },
+    ]);
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('Gold');
+  });
+
+  it('should fail when heat is required but not provided', () => {
+    const result = ReactionEngine.react([
+      { id: 'C', count: 1 },
+      { id: 'O', count: 2 },
+    ]); // No heat
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('temperature');
+  });
+
+  it('should fail when catalyst is required but not provided', () => {
+    const result = ReactionEngine.react(
+      [
+        { id: 'C', count: 1 },
+        { id: 'H', count: 4 },
+      ],
+      { minTemp: 500 }, // Heat provided, but catalyst (Fe) missing
+    );
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('catalyst');
+  });
+
+  it('should fail when energy is required but not provided', () => {
+    const result = ReactionEngine.react([
+      { id: 'H2O', count: 1 },
+    ]); // Electrolysis needs energy
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('energy');
+  });
+
+  it('should fail for unknown substances', () => {
+    const result = ReactionEngine.react([
+      { id: 'Unobtainium', count: 1 },
+      { id: 'Na', count: 1 },
+    ]);
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('Unknown substance');
+  });
+
+  it('should fail for same element with itself', () => {
+    const result = ReactionEngine.react([
+      { id: 'Fe', count: 1 },
+      { id: 'Fe', count: 1 },
+    ]);
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toBeDefined();
+  });
+
+  it('should suggest wrong proportions when elements match but counts differ', () => {
+    // H + O exists? No, H:1+O:1 doesn't but H:2+O:1 does
+    const result = ReactionEngine.react(
+      [
+        { id: 'H', count: 1 },
+        { id: 'O', count: 1 },
+      ],
+      { minTemp: 500 },
+    );
+    expect(result.success).toBe(false);
+    expect(result.failureReason).toContain('proportions');
+  });
+});
+
+// =============================================================================
+// REACTION ENGINE — METADATA
+// =============================================================================
+
+describe('ReactionEngine — metadata', () => {
+  it('should have 30+ registered reactions', () => {
+    expect(ReactionEngine.count()).toBeGreaterThanOrEqual(30);
+  });
+
+  it('should look up reactions by id', () => {
+    const thermite = ReactionEngine.getById('redox_thermite');
+    expect(thermite).toBeDefined();
+    expect(thermite!.type).toBe('redox');
+  });
+
+  it('every reaction should have both English and Russian descriptions', () => {
+    for (const r of ReactionEngine.getAll()) {
+      expect(r.description.length).toBeGreaterThan(10);
+      expect(r.descriptionRu.length).toBeGreaterThan(10);
+    }
+  });
+
+  it('every reaction should have valid reactants and products', () => {
+    for (const r of ReactionEngine.getAll()) {
+      expect(r.reactants.length).toBeGreaterThanOrEqual(1);
+      expect(r.products.length).toBeGreaterThanOrEqual(1);
+      for (const reactant of r.reactants) {
+        expect(reactant.count).toBeGreaterThan(0);
+        const exists =
+          ElementRegistry.isElement(reactant.id) || CompoundRegistry.isCompound(reactant.id);
+        expect(exists, `Reactant "${reactant.id}" in reaction "${r.id}" not found`).toBe(true);
+      }
+      for (const product of r.products) {
+        expect(product.count).toBeGreaterThan(0);
+        const exists =
+          ElementRegistry.isElement(product.id) || CompoundRegistry.isCompound(product.id);
+        expect(exists, `Product "${product.id}" in reaction "${r.id}" not found`).toBe(true);
+      }
+    }
+  });
+});