feat: add emoji pool and difficulty-based selection

superpowers/src/game/emoji.ts

@@ -0,0 +1,17 @@
+import { Difficulty } from "../types";
+import { DIFFICULTY_CONFIGS } from "./constants";
+
+export const EMOJI_POOL: string[] = [
+  "🐶", "🐱", "🐭", "🐹", "🐰", "🦊", "🐻", "🐼",
+  "🐨", "🐯", "🦁", "🐮", "🐷", "🐸", "🐵", "🐔",
+  "🐧", "🐦", "🦆", "🦅", "🦉", "🦇", "🐺", "🐗",
+  "🐴", "🦄", "🐝", "🐛", "🦋", "🐌", "🐞", "🐢",
+  "🐍", "🦎", "🐙", "🦑", "🦐", "🦀", "🐡", "🐠",
+  "🐟", "🐬", "🐳", "🐊",
+];
+
+export function getEmojisForDifficulty(difficulty: Difficulty): string[] {
+  const count = DIFFICULTY_CONFIGS[difficulty].pairCount;
+  const shuffled = [...EMOJI_POOL].sort(() => Math.random() - 0.5);
+  return shuffled.slice(0, count);
+}

superpowers/tests/game/emoji.test.ts

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+import { describe, it, expect } from "vitest";
+import { EMOJI_POOL, getEmojisForDifficulty } from "../../src/game/emoji";
+
+describe("emoji", () => {
+  it("pool has at least 40 unique emoji", () => {
+    expect(EMOJI_POOL.length).toBeGreaterThanOrEqual(40);
+    expect(new Set(EMOJI_POOL).size).toBe(EMOJI_POOL.length);
+  });
+
+  it("returns correct count for easy", () => {
+    const emojis = getEmojisForDifficulty("easy");
+    expect(emojis.length).toBe(12);
+    expect(new Set(emojis).size).toBe(12);
+  });
+
+  it("returns correct count for medium", () => {
+    const emojis = getEmojisForDifficulty("medium");
+    expect(emojis.length).toBe(24);
+  });
+
+  it("returns correct count for hard", () => {
+    const emojis = getEmojisForDifficulty("hard");
+    expect(emojis.length).toBe(40);
+  });
+
+  it("returned emojis are a subset of the pool", () => {
+    const emojis = getEmojisForDifficulty("hard");
+    for (const e of emojis) {
+      expect(EMOJI_POOL).toContain(e);
+    }
+  });
+});