feat: add score calculation with speed bonus and combo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

superpowers/src/game/scoring.ts

@@ -0,0 +1,14 @@
+import { BASE_MATCH_SCORE, SPEED_BONUS_MAX, SPEED_BONUS_WINDOW_MS } from "./constants";
+
+export function calculateMatchScore(
+  msSinceLastMatch: number,
+  combo: number
+): number {
+  let speedBonus = 0;
+  if (msSinceLastMatch < SPEED_BONUS_WINDOW_MS) {
+    const ratio = 1 - msSinceLastMatch / SPEED_BONUS_WINDOW_MS;
+    speedBonus = Math.round(SPEED_BONUS_MAX * ratio);
+  }
+
+  return (BASE_MATCH_SCORE + speedBonus) * combo;
+}

superpowers/tests/game/scoring.test.ts

@@ -0,0 +1,31 @@
+import { describe, it, expect } from "vitest";
+import { calculateMatchScore } from "../../src/game/scoring";
+
+describe("calculateMatchScore", () => {
+  it("returns base score with no speed bonus and combo 1", () => {
+    const score = calculateMatchScore(10000, 1);
+    expect(score).toBe(100);
+  });
+
+  it("adds speed bonus for fast match", () => {
+    const score = calculateMatchScore(1000, 1);
+    expect(score).toBeGreaterThan(100);
+    expect(score).toBeLessThanOrEqual(150);
+  });
+
+  it("applies combo multiplier", () => {
+    const base = calculateMatchScore(10000, 1);
+    const combo3 = calculateMatchScore(10000, 3);
+    expect(combo3).toBe(base * 3);
+  });
+
+  it("combines speed bonus and combo", () => {
+    const score = calculateMatchScore(0, 2);
+    expect(score).toBe((100 + 50) * 2);
+  });
+
+  it("no speed bonus after window expires", () => {
+    const score = calculateMatchScore(6000, 1);
+    expect(score).toBe(100);
+  });
+});