* { margin:0; padding:0; box-sizing:border-box; }
body { font-family: -apple-system, sans-serif; background:#f5f5f5; padding-bottom:60px; }
.banner img { width:100%; display:block; }
.course-item { background:#fff; margin:10px; padding:15px; border-radius:8px; }
.course-item h4 { font-size:18px; }
.course-item p { color:#666; margin:8px 0; }
.buy-btn { background:#ff6600; color:#fff; border:none; padding:8px 20px; border-radius:20px; }
.tab-bar { position:fixed; bottom:0; left:0; right:0; display:flex; background:#fff; border-top:1px solid #ddd; }
.tab-item { flex:1; text-align:center; padding:10px 0; }
.tab-item.active { color:#ff6600; }