*{box-sizing:border-box}body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;background:#f5f6f8;color:#222}
a{text-decoration:none;color:inherit}
.app{max-width:980px;margin:0 auto;padding:14px}
.mobile-shell{max-width:430px;margin:0 auto;background:#fff;min-height:100vh;box-shadow:0 0 0 1px rgba(0,0,0,.04)}
.section-title{font-size:18px;font-weight:700;margin:18px 14px 12px}
.carousel{position:relative;overflow:hidden;border-radius:0 0 16px 16px}
.carousel-track{display:flex;transition:transform .4s ease}
.carousel-slide{min-width:100%;height:180px;background:#dfe9dd}
.carousel-slide img{width:100%;height:100%;object-fit:cover;display:block}
.carousel-dots{position:absolute;bottom:10px;left:0;right:0;display:flex;justify-content:center;gap:7px}
.carousel-dots button{width:8px;height:8px;border:none;border-radius:999px;background:rgba(255,255,255,.6);padding:0;cursor:pointer}
.carousel-dots button.active{background:#fff;width:18px}
.course-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px;padding:0 14px 18px}
.course-card{background:#fff;border-radius:12px;overflow:hidden;box-shadow:0 2px 10px rgba(0,0,0,.06)}
.thumb-wrap{position:relative;height:116px;background:#eef1f5}
.thumb-wrap img{width:100%;height:100%;object-fit:cover;display:block}
.video-badge{position:absolute;right:8px;bottom:8px;padding:4px 7px;border-radius:999px;background:rgba(0,0,0,.55);color:#fff;font-size:12px}
.course-body{padding:10px}
.course-title{font-size:16px;font-weight:700;line-height:1.35;min-height:43px}
.course-meta{display:flex;justify-content:space-between;align-items:center;margin-top:8px;font-size:13px;color:#9aa0a6}
.price-free{color:#ff6388;font-weight:700}
.price-paid{color:#ff8a00;font-weight:700}
.hero-card{padding:14px}
.hero-media{position:relative;border-radius:18px;overflow:hidden;background:#111;display:block}
.hero-media img{width:100%;height:220px;display:block;object-fit:cover}
.play-button{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;background:linear-gradient(to bottom,rgba(0,0,0,.1),rgba(0,0,0,.26))}
.play-button span{width:72px;height:72px;border-radius:50%;display:flex;align-items:center;justify-content:center;background:rgba(255,255,255,.92);font-size:32px;color:#111;box-shadow:0 8px 24px rgba(0,0,0,.2)}
.hero-title{font-size:27px;font-weight:800;line-height:1.25;margin:14px 0 8px}
.hero-sub{display:flex;justify-content:space-between;align-items:center;color:#80868b;font-size:14px}
.tabs{display:flex;padding:0 14px;border-bottom:1px solid #efefef;margin-top:6px}
.tab-active{padding:12px 0;color:#2668ff;font-weight:700;border-bottom:3px solid #2668ff}
.lecturer{display:flex;justify-content:space-between;align-items:center;padding:14px}
.lecturer-left{display:flex;gap:12px;align-items:center}
.avatar{width:46px;height:46px;border-radius:50%;background:#d9dee5;display:flex;align-items:center;justify-content:center;font-weight:700;color:#555}
.lecturer-name{font-size:17px;font-weight:700}
.lecturer-bio{font-size:13px;color:#8a8f98;margin-top:4px}
.outline-btn{padding:10px 14px;border-radius:999px;background:#eef3ff;color:#3a63ff;font-size:14px;font-weight:700}
.detail-list{padding:0 18px 20px;margin:0;list-style:none}
.detail-list li{position:relative;padding-left:16px;margin:10px 0;line-height:1.7;color:#2f3338}
.detail-list li::before{content:"";position:absolute;left:0;top:11px;width:6px;height:6px;border-radius:50%;background:#4c74ff}
.download-btn{display:block;margin:0 14px 18px;padding:14px 16px;text-align:center;border-radius:14px;background:#1f6fff;color:#fff;font-size:16px;font-weight:800}
.modal{position:fixed;inset:0;background:rgba(0,0,0,.72);display:none;align-items:center;justify-content:center;padding:20px;z-index:1000}
.modal.active{display:flex}
.modal-box{width:min(900px,100%);background:#000;border-radius:16px;overflow:hidden;position:relative}
.modal-close{position:absolute;right:10px;top:10px;width:36px;height:36px;border:none;border-radius:50%;background:rgba(255,255,255,.18);color:#fff;font-size:20px;cursor:pointer;z-index:2}
.modal video{width:100%;display:block;background:#000}
.admin-wrap{max-width:1100px;margin:0 auto;padding:20px}
.admin-card{background:#fff;border-radius:16px;padding:18px;box-shadow:0 8px 28px rgba(0,0,0,.06);margin-bottom:18px}
.admin-topbar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap}
.flash{padding:12px 14px;border-radius:12px;margin-bottom:14px}
.flash.success{background:#e9f9ee;color:#18794e}
.flash.error{background:#fff1f1;color:#c62828}
.btn{display:inline-block;padding:10px 14px;border:none;border-radius:10px;background:#246bff;color:#fff;cursor:pointer;font-weight:700}
.btn.gray{background:#6c7580}
.btn.red{background:#e53935}
.btn.light{background:#eef3ff;color:#246bff}
.table-wrap{overflow:auto}
table{width:100%;border-collapse:collapse}
th,td{padding:12px 10px;border-bottom:1px solid #edf0f2;text-align:left;font-size:14px;vertical-align:top}
form label{display:block;font-size:14px;font-weight:700;margin:12px 0 6px}
form input[type=text],form input[type=number],form input[type=url],form input[type=password],form input[type=file],form textarea{width:100%;padding:12px;border:1px solid #dce1e7;border-radius:10px;font-size:14px;background:#fff}
form textarea{min-height:130px;resize:vertical}
.helper{font-size:12px;color:#7c8590;margin-top:4px}
.preview{width:120px;border-radius:10px;margin-top:10px;border:1px solid #edf0f2}
.nav-links{display:flex;gap:10px;flex-wrap:wrap}
.login-shell{min-height:100vh;display:flex;align-items:center;justify-content:center;padding:20px}
.login-card{width:min(430px,100%);background:#fff;border-radius:18px;padding:24px;box-shadow:0 12px 32px rgba(0,0,0,.08)}
.muted{color:#7c8590;font-size:13px}
@media (max-width:520px){.hero-title{font-size:24px}.course-title{font-size:15px}}