diff --git a/.gitignore b/.gitignore
index 6a6c6fc..51fa152 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,6 +10,7 @@ lerna-debug.log*
 node_modules
 dist
 dist-ssr
+.vite
 *.local
 
 # Editor directories and files
diff --git a/src/core/cards/card-library.ts b/src/core/cards/card-library.ts
index 8449ed7..3043124 100644
--- a/src/core/cards/card-library.ts
+++ b/src/core/cards/card-library.ts
@@ -1,82 +1,21 @@
 import type { CardData } from './card.types';
+import { ALL_CARDS } from './definitions';
 
 /**
- * Central card library. All card definitions live here, keyed by id.
- * Content is data — add cards by adding entries, not code paths.
+ * Central card library. Card *definitions* live one-per-file under ./definitions
+ * and are registered in ./definitions/index.ts; this module indexes them by id.
+ * Content is data — add cards by adding a file, not by editing code paths here.
  */
-export const CARD_LIBRARY: Record<string, CardData> = {
-    strike: {
-        id: 'strike',
-        name: 'Strike',
-        type: 'attack',
-        rarity: 'starter',
-        cost: 1,
-        target: 'enemy',
-        description: 'Deal 6 damage.',
-        effect: { damage: 6 },
-    },
-    defend: {
-        id: 'defend',
-        name: 'Defend',
-        type: 'skill',
-        rarity: 'starter',
-        cost: 1,
-        target: 'self',
-        description: 'Gain 5 block.',
-        effect: { block: 5 },
-    },
-    bash: {
-        id: 'bash',
-        name: 'Bash',
-        type: 'attack',
-        rarity: 'starter',
-        cost: 2,
-        target: 'enemy',
-        description: 'Deal 10 damage.',
-        effect: { damage: 10 },
-    },
-    quick_slash: {
-        id: 'quick_slash',
-        name: 'Quick Slash',
-        type: 'attack',
-        rarity: 'common',
-        cost: 1,
-        target: 'enemy',
-        description: 'Deal 4 damage. Draw 1 card.',
-        effect: { damage: 4, draw: 1 },
-    },
-    cleave: {
-        id: 'cleave',
-        name: 'Cleave',
-        type: 'attack',
-        rarity: 'common',
-        cost: 1,
-        target: 'all-enemies',
-        description: 'Deal 8 damage to ALL enemies.',
-        effect: { damage: 8 },
-    },
-    flurry: {
-        id: 'flurry',
-        name: 'Flurry',
-        type: 'attack',
-        rarity: 'uncommon',
-        cost: 1,
-        target: 'enemy',
-        description: 'Deal 3 damage 3 times.',
-        effect: { damage: 3, hits: 3 },
-    },
-    adrenaline: {
-        id: 'adrenaline',
-        name: 'Adrenaline',
-        type: 'skill',
-        rarity: 'uncommon',
-        cost: 0,
-        target: 'none',
-        description: 'Gain 1 energy. Draw 2 cards. Exhaust.',
-        effect: { energy: 1, draw: 2 },
-        exhaust: true,
-    },
-};
+export const CARD_LIBRARY: Record<string, CardData> = buildLibrary();
+
+function buildLibrary(): Record<string, CardData> {
+    const library: Record<string, CardData> = {};
+    for (const card of ALL_CARDS) {
+        if (library[card.id]) throw new Error(`Duplicate card id: ${card.id}`);
+        library[card.id] = card;
+    }
+    return library;
+}
 
 /** Look up a card definition by id; throws early on typos rather than failing silently. */
 export function getCard(id: string): CardData {
diff --git a/src/core/cards/definitions/adrenaline.ts b/src/core/cards/definitions/adrenaline.ts
new file mode 100644
index 0000000..f93d1db
--- /dev/null
+++ b/src/core/cards/definitions/adrenaline.ts
@@ -0,0 +1,13 @@
+import type { CardData } from '../card.types';
+
+export const adrenaline: CardData = {
+    id: 'adrenaline',
+    name: 'Adrenaline',
+    type: 'skill',
+    rarity: 'uncommon',
+    cost: 0,
+    target: 'none',
+    description: 'Gain 1 energy. Draw 2 cards. Exhaust.',
+    effect: { energy: 1, draw: 2 },
+    exhaust: true,
+};
diff --git a/src/core/cards/definitions/bash.ts b/src/core/cards/definitions/bash.ts
new file mode 100644
index 0000000..050b3cc
--- /dev/null
+++ b/src/core/cards/definitions/bash.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const bash: CardData = {
+    id: 'bash',
+    name: 'Bash',
+    type: 'attack',
+    rarity: 'starter',
+    cost: 2,
+    target: 'enemy',
+    description: 'Deal 10 damage.',
+    effect: { damage: 10 },
+};
diff --git a/src/core/cards/definitions/cleave.ts b/src/core/cards/definitions/cleave.ts
new file mode 100644
index 0000000..5156070
--- /dev/null
+++ b/src/core/cards/definitions/cleave.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const cleave: CardData = {
+    id: 'cleave',
+    name: 'Cleave',
+    type: 'attack',
+    rarity: 'common',
+    cost: 1,
+    target: 'all-enemies',
+    description: 'Deal 8 damage to ALL enemies.',
+    effect: { damage: 8 },
+};
diff --git a/src/core/cards/definitions/defend.ts b/src/core/cards/definitions/defend.ts
new file mode 100644
index 0000000..8e246bb
--- /dev/null
+++ b/src/core/cards/definitions/defend.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const defend: CardData = {
+    id: 'defend',
+    name: 'Defend',
+    type: 'skill',
+    rarity: 'starter',
+    cost: 1,
+    target: 'self',
+    description: 'Gain 5 block.',
+    effect: { block: 5 },
+};
diff --git a/src/core/cards/definitions/flurry.ts b/src/core/cards/definitions/flurry.ts
new file mode 100644
index 0000000..1bbf399
--- /dev/null
+++ b/src/core/cards/definitions/flurry.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const flurry: CardData = {
+    id: 'flurry',
+    name: 'Flurry',
+    type: 'attack',
+    rarity: 'uncommon',
+    cost: 1,
+    target: 'enemy',
+    description: 'Deal 3 damage 3 times.',
+    effect: { damage: 3, hits: 3 },
+};
diff --git a/src/core/cards/definitions/index.ts b/src/core/cards/definitions/index.ts
new file mode 100644
index 0000000..d97cc0d
--- /dev/null
+++ b/src/core/cards/definitions/index.ts
@@ -0,0 +1,24 @@
+import type { CardData } from '../card.types';
+
+import { strike } from './strike';
+import { defend } from './defend';
+import { bash } from './bash';
+import { quickSlash } from './quick-slash';
+import { cleave } from './cleave';
+import { flurry } from './flurry';
+import { adrenaline } from './adrenaline';
+
+/**
+ * Card manifest. Every card definition is registered here exactly once.
+ * Adding a card = create ./<card>.ts, then add one import + one array entry.
+ * The library (card-library.ts) keys these by id and enforces uniqueness.
+ */
+export const ALL_CARDS: readonly CardData[] = [
+    strike,
+    defend,
+    bash,
+    quickSlash,
+    cleave,
+    flurry,
+    adrenaline,
+];
diff --git a/src/core/cards/definitions/quick-slash.ts b/src/core/cards/definitions/quick-slash.ts
new file mode 100644
index 0000000..802fcd4
--- /dev/null
+++ b/src/core/cards/definitions/quick-slash.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const quickSlash: CardData = {
+    id: 'quick_slash',
+    name: 'Quick Slash',
+    type: 'attack',
+    rarity: 'common',
+    cost: 1,
+    target: 'enemy',
+    description: 'Deal 4 damage. Draw 1 card.',
+    effect: { damage: 4, draw: 1 },
+};
diff --git a/src/core/cards/definitions/strike.ts b/src/core/cards/definitions/strike.ts
new file mode 100644
index 0000000..eb8fa29
--- /dev/null
+++ b/src/core/cards/definitions/strike.ts
@@ -0,0 +1,12 @@
+import type { CardData } from '../card.types';
+
+export const strike: CardData = {
+    id: 'strike',
+    name: 'Strike',
+    type: 'attack',
+    rarity: 'starter',
+    cost: 1,
+    target: 'enemy',
+    description: 'Deal 6 damage.',
+    effect: { damage: 6 },
+};