阶段1：项目初始化完成

- 创建基础项目结构
- 实现 HTML/CSS/JS 基础框架
- 配置游戏界面和样式

Closes #1

style.css

@@ -0,0 +1,177 @@
+* {
+    margin: 0;
+    padding: 0;
+    box-sizing: border-box;
+}
+
+body {
+    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
+    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+    min-height: 100vh;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    padding: 20px;
+}
+
+.container {
+    background: rgba(255, 255, 255, 0.95);
+    border-radius: 20px;
+    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
+    padding: 30px;
+    max-width: 600px;
+    width: 100%;
+}
+
+header {
+    text-align: center;
+    margin-bottom: 20px;
+}
+
+header h1 {
+    color: #333;
+    font-size: 2.5em;
+    margin-bottom: 10px;
+}
+
+.score-board {
+    font-size: 1.5em;
+    color: #764ba2;
+    font-weight: bold;
+}
+
+#score {
+    color: #e74c3c;
+}
+
+main {
+    text-align: center;
+}
+
+.game-controls {
+    margin-bottom: 20px;
+    display: flex;
+    justify-content: center;
+    gap: 10px;
+}
+
+.btn {
+    padding: 10px 20px;
+    font-size: 16px;
+    border: none;
+    border-radius: 8px;
+    cursor: pointer;
+    transition: all 0.3s ease;
+    font-weight: bold;
+}
+
+#startBtn {
+    background: #27ae60;
+    color: white;
+}
+
+#startBtn:hover {
+    background: #229954;
+}
+
+#pauseBtn {
+    background: #f39c12;
+    color: white;
+}
+
+#pauseBtn:hover {
+    background: #e67e22;
+}
+
+#pauseBtn:disabled {
+    background: #ccc;
+    cursor: not-allowed;
+}
+
+#resetBtn {
+    background: #e74c3c;
+    color: white;
+}
+
+#resetBtn:hover {
+    background: #c0392b;
+}
+
+.difficulty-selector {
+    margin-bottom: 20px;
+    font-size: 1.1em;
+    color: #333;
+}
+
+#difficulty {
+    padding: 5px 10px;
+    font-size: 16px;
+    border: 2px solid #764ba2;
+    border-radius: 5px;
+    background: white;
+    cursor: pointer;
+}
+
+#gameCanvas {
+    background: #2c3e50;
+    border: 4px solid #34495e;
+    border-radius: 10px;
+    display: block;
+    margin: 0 auto 20px;
+    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
+}
+
+.game-info {
+    text-align: left;
+    background: #f8f9fa;
+    padding: 15px;
+    border-radius: 8px;
+    border-left: 4px solid #764ba2;
+}
+
+.game-info h3 {
+    color: #333;
+    margin-bottom: 10px;
+}
+
+.game-info ul {
+    list-style: none;
+    padding-left: 0;
+}
+
+.game-info li {
+    padding: 5px 0;
+    color: #555;
+    position: relative;
+    padding-left: 20px;
+}
+
+.game-info li::before {
+    content: "🎮";
+    position: absolute;
+    left: 0;
+}
+
+@media (max-width: 600px) {
+    .container {
+        padding: 20px;
+    }
+
+    header h1 {
+        font-size: 1.8em;
+    }
+
+    #gameCanvas {
+        width: 100%;
+        height: auto;
+    }
+
+    .game-controls {
+        flex-wrap: wrap;
+    }
+
+    .btn {
+        flex: 1;
+        min-width: 80px;
+    }
+}