feat: add comprehensive Playwright testing suite with visual regression

- Add Playwright configuration with multi-browser testing
- Create basic functionality tests for game mechanics
- Add gameplay tests with keyboard and touch interactions
- Implement visual regression testing with screenshots
- Add environment-specific tests for dev/staging/prod
- Include health endpoint and security header validation
- Set up test infrastructure for CI/CD pipeline

tests/basic.spec.ts

@@ -0,0 +1,58 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('2048 Game - Basic Functionality', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.goto('/');
+    await page.waitForLoadState('networkidle');
+  });
+
+  test('should load the game successfully', async ({ page }) => {
+    // Check title
+    await expect(page).toHaveTitle(/2048/);
+    
+    // Check main elements are present
+    await expect(page.locator('h1')).toContainText('2048');
+    await expect(page.locator('.game-container')).toBeVisible();
+    await expect(page.locator('.grid-container')).toBeVisible();
+    
+    // Check score displays
+    await expect(page.locator('#score')).toBeVisible();
+    await expect(page.locator('#best')).toBeVisible();
+  });
+
+  test('should show environment badge', async ({ page }) => {
+    const envBadge = page.locator('#env-badge');
+    await expect(envBadge).toBeVisible();
+    
+    // Should have one of the environment classes
+    const badgeClass = await envBadge.getAttribute('class');
+    expect(badgeClass).toMatch(/(development|staging|production)/);
+  });
+
+  test('should have initial tiles on game start', async ({ page }) => {
+    // Should have at least 2 tiles initially
+    const tiles = page.locator('.tile');
+    await expect(tiles).toHaveCount(2);
+    
+    // Tiles should have values 2 or 4
+    const tileTexts = await tiles.allTextContents();
+    tileTexts.forEach(text => {
+      expect(['2', '4']).toContain(text);
+    });
+  });
+
+  test('should restart game when restart button is clicked', async ({ page }) => {
+    const restartButton = page.locator('#restart-button');
+    await expect(restartButton).toBeVisible();
+    
+    // Click restart
+    await restartButton.click();
+    
+    // Should have exactly 2 tiles after restart
+    const tiles = page.locator('.tile');
+    await expect(tiles).toHaveCount(2);
+    
+    // Score should be reset to 0
+    await expect(page.locator('#score')).toHaveText('0');
+  });
+});