refactor: translate comments and improve code readability

Update comments from Chinese to English for better international collaboration
Standardize comment style across HTML, CSS and JavaScript files
Remove unnecessary comments about global variables

js/script.js

@@ -1,4 +1,3 @@
-// 全局变量
 let videos = [
   {
     "id": 1,
@@ -476,7 +475,7 @@ let videos = [
 ];
 let currentCategory = 'All';
 
-// DOM 元素
+// DOM elements
 const searchInput = document.querySelector('.search-input');
 const searchBtn = document.querySelector('.search-btn');
 const searchResults = document.querySelector('.search-results');
@@ -505,13 +504,13 @@ function renderVideos() {
     videoGrid.innerHTML = '';
     shortsGrid.innerHTML = '';
     
-    // 渲染长视频
+    // Render long videos
     videosOnly.forEach(video => {
         const videoCard = createVideoCard(video);
         videoGrid.appendChild(videoCard);
     });
     
-    // 渲染短视频
+    // Render shorts videos
     shortsOnly.forEach(video => {
         const shortsCard = createShortsCard(video);
         shortsGrid.appendChild(shortsCard);