UI优化：美化顶部按钮为圆形图标，添加交互功能

grid-study/styles.css

@@ -55,20 +55,27 @@ body {
 }
 
 .top-bar__button {
-    padding: 8px 16px;
-    border: 1px solid rgba(0, 0, 0, 0.1);
-    border-radius: 8px;
-    background-color: rgba(255, 255, 255, 0.5);
-    backdrop-filter: blur(5px);
+    width: 40px;
+    height: 40px;
+    padding: 0;
+    border: none;
+    border-radius: 50%;
+    background-color: transparent;
     cursor: pointer;
     font-size: 14px;
     transition: var(--transition);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    color: #333;
+}
+
+.top-bar__button span {
+    display: none;
 }
 
 .top-bar__button:hover {
-    background-color: rgba(255, 255, 255, 0.8);
-    transform: translateY(-2px);
-    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
+    background-color: rgba(0, 0, 0, 0.05);
 }
 
 .top-bar__button:active {
@@ -386,11 +393,44 @@ body {
 }
 
 .task-item input[type="checkbox"] {
-    width: 18px;
-    height: 18px;
+    appearance: none;
+    -webkit-appearance: none;
+    width: 20px;
+    height: 20px;
+    border: 2px solid #c7c7cc;
+    border-radius: 50%; /* 圆形复选框 */
     margin: 0;
-    accent-color: #0071e3;
+    outline: none;
     cursor: pointer;
+    position: relative;
+    transition: all 0.2s ease;
+    flex-shrink: 0;
+}
+
+.task-item input[type="checkbox"]:checked {
+    background-color: #0071e3;
+    border-color: #0071e3;
+}
+
+.task-item input[type="checkbox"]:checked::after {
+    content: '';
+    position: absolute;
+    top: 45%;
+    left: 50%;
+    width: 9px;
+    height: 5px;
+    border-left: 2px solid white;
+    border-bottom: 2px solid white;
+    transform: translate(-50%, -50%) rotate(-45deg);
+}
+
+.task-item input[type="checkbox"]:hover {
+    border-color: #0071e3;
+    background-color: rgba(0, 113, 227, 0.05);
+}
+
+.task-item input[type="checkbox"]:checked:hover {
+    background-color: #0077ed;
 }
 
 .task-content {