Standardizes UI with CSS variables and refactors styles

Introduces CSS custom properties for unified colors, border, and radius,
simplifying style management and improving maintainability. Refactors
timestamp and datetime converter styles to use these variables for
consistency. Enhances visual feedback with hover effects and minor
typography adjustments. Updates a timer ref type annotation for clarity
and adds a container class for better structure.

src/App.css

@@ -11,6 +11,20 @@ body {
     overflow: auto;
 }
 
+:root {
+    /* 统一圆角变量 */
+    --radius: 8px;
+    /* 统一背景颜色变量 */
+    --bg-color: #fafafa;
+    /* 统一文字颜色变量 */
+    --text-color: #333333;
+    /* 统一按钮颜色变量 */
+    --btn-bg: #e0e0e0;
+    /* 统一按钮文字颜色变量 */
+    --btn-text: #333333;
+    --border: 1px solid #e0e0e0;
+}
+
 .app {
     max-width: 800px;
     margin: 0 auto;
@@ -620,32 +634,25 @@ select {
 /* 时间戳组件样式 */
 .timestamp-container {
     padding: 20px;
-    border: 1px solid #e0e0e0;
-    border-radius: 8px;
-    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
-    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
+    border: var(--border);
+    border-radius: var(--radius);
+    background: var(--bg-color);
     margin: 20px 0;
 }
 
-.timestamp-title {
-    color: #2c3e50;
-    font-size: 1.5rem;
-    margin-bottom: 20px;
-    text-align: center;
-    font-weight: 600;
+.timestamp-container:hover {
+    box-shadow: 4px 4px 12px 8px rgba(0, 0, 0, 0.1);
+    transition: box-shadow 0.3s ease;
 }
 
+/* 时间戳显示区域 */
 .timestamp-display {
     display: flex;
     align-items: center; /* 垂直居中 */
     justify-content: center; /* 横向居中 */
     gap: 10px;
     margin-bottom: 25px;
-    padding: 15px;
-    background: white;
-    border-radius: 8px;
-    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.1);
-    min-height: 80px;
+    border-radius: var(--radius);
     overflow-x: auto;
     overflow-y: hidden;
     white-space: nowrap;
@@ -653,8 +660,8 @@ select {
 
 .timestamp-value {
     font-size: 2.5rem;
-    font-weight: 700;
-    color: #3498db;
+    font-weight: 600;
+    color: var(--text-color);
     font-family: 'Courier New', monospace;
     text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.1);
     white-space: nowrap;
@@ -662,16 +669,15 @@ select {
 }
 
 .timestamp-unit {
-    font-size: 1.2rem;
-    color: #7f8c8d;
-    font-weight: 500;
+    font-size: 1rem;
+    color: var(--text-color);
+    font-weight: 400;
 }
 
 .timestamp-controls {
     display: flex;
     gap: 12px;
     justify-content: center;
-    margin-bottom: 20px;
     flex-wrap: wrap;
 }
 
@@ -842,13 +848,18 @@ select {
 /* 日期时间转换器样式 */
 .datetime-converter {
     padding: 20px;
-    border: 1px solid #e0e0e0;
+    border: var(--border);
     border-radius: 8px;
-    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
+    background: var(--bg-color);
     box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
     margin: 20px 0;
 }
 
+.datetime-converter:hover {
+    box-shadow: 4px 4px 12px 8px rgba(0, 0, 0, 0.1);
+    transition: box-shadow 0.3s ease;
+}
+
 .converter-title {
     color: #2c3e50;
     font-size: 1.5rem;
@@ -877,7 +888,7 @@ select {
     border: 1px solid #ddd;
     border-radius: 8px;
     font-size: 0.95rem;
-    font-family: 'Courier New', monospace;
+    font-weight: 400;
     background: white;
     transition: border-color 0.2s ease;
     width: auto !important;

src/components/TimestampExecution.js

@@ -29,7 +29,7 @@ export function TimestampExecution() {
   /** @type {[boolean, function]} 时间戳是否正在自动更新 */
   const [isRunningTimestamp, setIsRunningTimestamp] = useState(true);
   
-  /** @type {React.MutableRefObject<NodeJS.Timeout|null>} 定时器引用，用于清理 */
+  /** @type {React.RefObject<NodeJS.Timeout | null>} 定时器引用，用于清理 */
   const timerRef = useRef(null);
   
   /**

src/pages/TimestampPage.js

@@ -5,7 +5,7 @@ import {TimestampExecution} from "../components/TimestampExecution";
 
 const TimestampPage = () => {
   
-  return (<div>
+  return (<div className="timestamp-utils">
     <TimestampExecution/>
     <TimestampToDatetime/>
     <DatetimeToTimestamp/>