/* =========================================================
   奇妙物理 · 全站样式
   改颜色只需改下面 :root 里的变量
   ========================================================= */

:root{
  --navy:#0f2542;
  --navy-2:#16345c;
  --blue:#1a6dff;
  --blue-d:#0f52c8;
  --blue-l:#e8f1ff;
  --green:#12a15c;
  --green-l:#e6f7ee;
  --purple:#7b3ff2;
  --orange:#f59e0b;
  --danger:#d92d20;
  --text:#0f2542;
  --text-2:#475569;
  --text-3:#64748b;
  --line:#e3e9f2;
  --bg:#f6f8fc;
  --card:#ffffff;
  --radius:16px;
  --radius-s:10px;
  --shadow:0 6px 24px rgba(15,37,66,.08);
  --shadow-lg:0 16px 40px rgba(15,37,66,.14);
  --max:1120px;
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:"Microsoft YaHei","PingFang SC","Helvetica Neue",Arial,sans-serif;
  background:var(--bg);color:var(--text);line-height:1.7;
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;text-decoration:none}
img{max-width:100%}
button{font-family:inherit;cursor:pointer;border:none;background:none;color:inherit}
input,textarea,select{font-family:inherit}

.wrap{max-width:var(--max);margin:0 auto;padding:0 20px}
.hidden{display:none !important}
.muted{color:var(--text-3);font-size:14px}
.center{text-align:center}

/* 页面顶部提示条（仅原型/演示环境出现） */
.demo-bar{
  background:#111c2e;color:#cfe0ff;font-size:13px;padding:6px 20px;text-align:center;
}
.demo-bar b{color:#7fb2ff}

/* ---------------- 顶部导航 ---------------- */
header.top{
  position:sticky;top:0;z-index:50;background:rgba(255,255,255,.95);
  backdrop-filter:blur(8px);border-bottom:1px solid var(--line);
}
.top-in{display:flex;align-items:center;gap:26px;height:66px}
.logo{display:flex;align-items:center;gap:10px;font-size:20px;font-weight:800;letter-spacing:.5px;flex:0 0 auto}
.logo img{width:34px;height:34px;display:block;border-radius:10px}
nav.main{display:flex;gap:20px;font-size:15px;color:#334155}
nav.main a{padding:4px 2px;border-bottom:2px solid transparent}
nav.main a:hover{color:var(--blue)}
nav.main a.on{color:var(--blue);border-bottom-color:var(--blue);font-weight:700}
.top-right{margin-left:auto;display:flex;align-items:center;gap:12px}
.btn-login{
  border:1px solid var(--blue);color:var(--blue);background:#fff;
  padding:7px 18px;border-radius:999px;font-size:14px;font-weight:600;
}
.btn-login:hover{background:var(--blue-l)}
.btn-admin{background:var(--blue);color:#fff;padding:8px 18px;border-radius:999px;font-size:14px;font-weight:600}
.btn-admin:hover{background:var(--blue-d)}
.nav-toggle{display:none;font-size:22px;line-height:1;padding:4px 8px;border-radius:8px}
.nav-toggle:hover{background:var(--bg)}

/* ---------------- 通用区块 ---------------- */
.sec{padding:56px 0}
.sec.tight{padding-top:8px}
.sec-head{text-align:center;margin-bottom:32px}
.sec-head h2{font-size:27px;font-weight:800;letter-spacing:.5px}
.sec-head p{color:var(--text-3);font-size:15px;margin-top:8px}
.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);border:1px solid var(--line)}
.btn-primary{
  display:inline-block;background:var(--blue);color:#fff;padding:13px 34px;
  border-radius:999px;font-size:16px;font-weight:700;box-shadow:0 8px 20px rgba(26,109,255,.28);
}
.btn-primary:hover{background:var(--blue-d)}
.btn-line{
  display:inline-block;border:1px solid rgba(255,255,255,.55);color:#fff;
  padding:12px 26px;border-radius:999px;font-size:15px;
}
.btn-line:hover{background:rgba(255,255,255,.14)}
.tag{display:inline-block;font-size:12px;padding:2px 9px;border-radius:999px;background:var(--blue-l);color:var(--blue-d);font-weight:600}
.crumb{font-size:13px;color:var(--text-3);padding:20px 0 0}
.crumb a{color:var(--blue)}
.crumb a:hover{text-decoration:underline}
.page-head{padding:14px 0 4px}
.page-head h1{font-size:30px;font-weight:800}
.page-head p{color:var(--text-3);font-size:15px;margin-top:8px}

/* 加载骨架 */
.skeleton{
  background:linear-gradient(90deg,#eef2f7 25%,#f7fafd 37%,#eef2f7 63%);
  background-size:400% 100%;animation:sk 1.3s ease infinite;border-radius:12px;
}
@keyframes sk{0%{background-position:100% 50%}100%{background-position:0 50%}}

/* ---------------- 首页 Hero ---------------- */
.hero{
  background:linear-gradient(160deg,#0b1f3a 0%,#123a66 52%,#0b1f3a 120%);
  color:#fff;padding:70px 0 78px;position:relative;overflow:hidden;
}
.hero::after{
  content:"";position:absolute;right:-140px;top:-100px;width:460px;height:460px;border-radius:50%;
  background:radial-gradient(circle,rgba(96,160,255,.32),transparent 65%);
}
.hero::before{
  content:"";position:absolute;left:-120px;bottom:-160px;width:380px;height:380px;border-radius:50%;
  background:radial-gradient(circle,rgba(18,161,92,.22),transparent 65%);
}
.hero .wrap{position:relative;z-index:1}
.hero h1{font-size:52px;font-weight:900;letter-spacing:3px;line-height:1.18}
.hero .slogan{font-size:19px;margin-top:16px;color:#d6e6ff}
.hero .lead{margin-top:14px;max-width:660px;color:#a9c6ef;font-size:15px}
.hero .cta{margin-top:28px;display:flex;gap:14px;flex-wrap:wrap;align-items:center}
.hero-stats{display:flex;gap:38px;margin-top:38px;flex-wrap:wrap}
.hero-stats b{display:block;font-size:24px;font-weight:800}
.hero-stats span{font-size:13px;color:#a9c6ef}

/* ---------------- 关于本站 ---------------- */
.about-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.about-grid .card{padding:26px}
.about-grid h3{font-size:17px;margin-bottom:10px}
.about-grid p{font-size:14px;color:var(--text-2)}
.about-note{
  margin-top:22px;padding:20px 24px;border-left:4px solid var(--blue);
  background:#fff;border-radius:var(--radius-s);font-size:14px;color:var(--text-2);
}

/* ---------------- 课程入口卡片 ---------------- */
.entry-grid{display:grid;grid-template-columns:1fr 1fr;gap:24px}
.entry{
  text-align:left;border-radius:20px;color:#fff;position:relative;overflow:hidden;
  transition:transform .18s ease, box-shadow .18s ease;box-shadow:var(--shadow-lg);
  display:flex;flex-direction:column;background:#0f2542;
}
.entry:hover{transform:translateY(-4px);box-shadow:0 22px 44px rgba(15,37,66,.24)}
.entry img{display:block;width:100%;height:auto}
.entry .entry-body{padding:18px 24px 22px;flex:1;display:flex;flex-direction:column}
.entry h3{font-size:24px;font-weight:800;margin-bottom:8px}
.entry p{font-size:14px;color:rgba(255,255,255,.92);flex:1}
.entry .go{margin-top:16px;font-size:14px;font-weight:700}
.entry.wide{grid-column:1 / -1}

/* ---------------- 最新更新 ---------------- */
.new-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.new-item{padding:18px 20px;display:flex;gap:14px;align-items:center;text-align:left;width:100%}
.new-thumb{
  width:74px;height:52px;border-radius:10px;flex:0 0 auto;display:grid;place-items:center;
  background:linear-gradient(135deg,#dce9ff,#b9d4ff);color:var(--blue-d);font-size:20px
}
.new-item h4{font-size:15px;font-weight:700}
.new-item .meta{font-size:12px;color:var(--text-3)}

/* ---------------- 直播板块 ---------------- */
.live-card{padding:26px 28px;display:flex;gap:24px;align-items:center;flex-wrap:wrap}
.live-card .ico{font-size:44px}
.live-card .live-info{flex:1;min-width:250px}
.live-card .live-info b{font-size:19px}
.live-row{display:flex;align-items:center;gap:10px;flex-wrap:wrap}

/* ---------------- 留言区 ---------------- */
.board-wrap{display:grid;grid-template-columns:360px 1fr;gap:24px;align-items:start}
.form-card{padding:24px}
.form-card h3{font-size:17px;margin-bottom:4px}
.form-card .hint{font-size:12px;color:var(--text-3);margin-bottom:16px}
.field{margin-bottom:13px}
.field label{display:block;font-size:13px;color:var(--text-2);margin-bottom:6px;font-weight:600}
.field input,.field textarea,.field select{
  width:100%;border:1px solid var(--line);border-radius:var(--radius-s);padding:10px 12px;
  font-size:14px;outline:none;background:#fbfcfe;color:var(--text);
}
.field input:focus,.field textarea:focus,.field select:focus{border-color:var(--blue);background:#fff}
.field textarea{min-height:104px;resize:vertical}
.field .err{color:var(--danger);font-size:12px;margin-top:5px;display:none}
.field.bad input,.field.bad textarea{border-color:var(--danger);background:#fff7f6}
.field.bad .err{display:block}
.btn-block{width:100%;background:var(--blue);color:#fff;padding:12px;border-radius:var(--radius-s);font-weight:700;font-size:15px}
.btn-block:hover{background:var(--blue-d)}
.btn-block:disabled{background:#94a3b8;cursor:not-allowed}
.form-tip{font-size:12px;color:var(--text-3);margin-top:10px;line-height:1.6}
.hp{position:absolute;left:-9999px;width:1px;height:1px;overflow:hidden}

.cmt{background:#fff;border:1px solid var(--line);border-radius:14px;padding:18px 20px;margin-bottom:14px}
.cmt-head{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.avatar{width:32px;height:32px;border-radius:50%;background:var(--blue-l);color:var(--blue-d);display:grid;place-items:center;font-weight:700;font-size:14px}
.cmt-name{font-weight:700;font-size:14px}
.cmt-time{font-size:12px;color:var(--text-3);margin-left:auto}
.cmt-body{margin:10px 0 8px;font-size:15px;color:#1e293b;white-space:pre-wrap;word-break:break-word}
.cmt-acts{display:flex;gap:16px;font-size:13px;color:var(--text-3);align-items:center}
.cmt-acts button:hover{color:var(--blue)}
.replies{margin-top:14px;padding-left:14px;border-left:2px solid var(--line);display:flex;flex-direction:column;gap:12px}
.reply{font-size:14px}
.reply-head{display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.reply-body{color:#334155;white-space:pre-wrap;word-break:break-word}
.badge-admin{background:var(--green-l);color:var(--green);font-size:12px;font-weight:700;padding:1px 9px;border-radius:999px}
.badge-user{background:#f1f5f9;color:var(--text-3);font-size:12px;padding:1px 9px;border-radius:999px}
.best{background:#fff8e6;color:#b7791f;font-size:12px;font-weight:700;padding:1px 9px;border-radius:999px}
.empty{text-align:center;color:var(--text-3);font-size:14px;padding:34px 10px}

/* ---------------- 课程页 ---------------- */
.grade-block{margin-top:24px;padding:24px;border-radius:var(--radius);background:#fff;border:1px solid var(--line);box-shadow:var(--shadow)}
.grade-head{display:flex;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:6px}
.grade-head h2{font-size:20px;font-weight:800}
.grade-head .pill{font-size:12px;background:var(--blue-l);color:var(--blue-d);padding:3px 10px;border-radius:999px;font-weight:600}
.grade-desc{font-size:14px;color:var(--text-3);margin-bottom:16px}
.lesson-row{
  display:flex;align-items:center;gap:16px;padding:14px 16px;border-radius:12px;
  border:1px solid var(--line);margin-bottom:10px;background:#fbfcfe;text-align:left;width:100%;
  transition:border-color .15s, background .15s;
}
.lesson-row:hover{border-color:#b9d4ff;background:#f4f8ff}
.lesson-row .no{
  width:30px;height:30px;border-radius:9px;background:var(--blue-l);color:var(--blue-d);
  display:grid;place-items:center;font-weight:700;font-size:14px;flex:0 0 auto
}
.lesson-row .ttl{font-size:15px;font-weight:600}
.lesson-row .sub{font-size:12px;color:var(--text-3)}
.lesson-row .dur{margin-left:auto;font-size:13px;color:var(--text-3);flex:0 0 auto;text-align:right}
.soon{background:#fef3f2;color:var(--danger);font-size:11px;padding:1px 8px;border-radius:999px;font-weight:700}

/* ---------------- 播放页 ---------------- */
.player{
  aspect-ratio:16/9;width:100%;border-radius:14px;background:linear-gradient(135deg,#132a49,#1c4372);
  color:#cfe0ff;display:grid;place-items:center;text-align:center;border:1px solid #24466f;overflow:hidden;
}
.player iframe{width:100%;height:100%;border:0;display:block}
.player .ico{font-size:46px}
.player p{font-size:14px;margin-top:10px;max-width:420px;padding:0 20px;color:#9fbde4}
.play-grid{display:grid;grid-template-columns:1fr 330px;gap:24px;margin-top:24px;align-items:start}
.info-card{padding:24px}
.info-card h2{font-size:22px;font-weight:800}
.info-card .meta{font-size:13px;color:var(--text-3);margin:8px 0 16px}
.info-card h3{font-size:16px;margin:18px 0 8px}
.info-card ul{padding-left:20px;font-size:14px;color:var(--text-2)}
.info-card li{margin-bottom:6px}
.side-card{padding:18px 20px}
.side-card h3{font-size:16px;margin-bottom:12px}
.side-list{display:flex;flex-direction:column;gap:8px;max-height:520px;overflow:auto}
.side-item{font-size:14px;padding:9px 12px;border-radius:9px;background:#f8fafd;text-align:left;border:1px solid transparent}
.side-item:hover{border-color:#b9d4ff;background:#f2f7ff}
.side-item.now{background:var(--blue-l);font-weight:700;color:var(--blue-d)}

/* ---------------- 登录页 ---------------- */
.login-card{max-width:430px;margin:60px auto;padding:34px}
.login-card h2{font-size:22px;font-weight:800;text-align:center}
.login-card p.sub{font-size:13px;color:var(--text-3);text-align:center;margin:8px 0 22px}
.login-foot{font-size:12px;color:var(--text-3);text-align:center;margin-top:16px;line-height:1.7}

/* ---------------- 客服悬浮按钮 + 弹窗 ---------------- */
.fab{
  position:fixed;right:22px;bottom:22px;z-index:80;
  background:linear-gradient(135deg,#07c160,#12a15c);color:#fff;
  padding:13px 20px;border-radius:999px;font-size:15px;font-weight:700;
  box-shadow:0 10px 26px rgba(7,193,96,.4);display:flex;align-items:center;gap:8px;
  transition:transform .16s ease;
}
.fab:hover{transform:translateY(-3px) scale(1.03)}
.fab .fab-dot{width:9px;height:9px;border-radius:50%;background:#fff;animation:pulse 1.9s infinite}
@keyframes pulse{
  0%{box-shadow:0 0 0 0 rgba(255,255,255,.85)}
  70%{box-shadow:0 0 0 12px rgba(255,255,255,0)}
  100%{box-shadow:0 0 0 0 rgba(255,255,255,0)}
}
.modal-mask{position:fixed;inset:0;background:rgba(8,20,38,.55);z-index:90;display:none;align-items:center;justify-content:center;padding:20px}
.modal-mask.show{display:flex}
.modal{background:#fff;border-radius:18px;max-width:360px;width:100%;padding:26px 24px 22px;position:relative;text-align:center;box-shadow:0 26px 60px rgba(0,0,0,.3)}
.modal h3{font-size:19px;font-weight:800;margin-bottom:6px}
.modal .sub{font-size:13px;color:var(--text-3);margin-bottom:16px}
.qr-box{width:190px;height:190px;margin:0 auto;border:1px solid var(--line);border-radius:14px;display:grid;place-items:center;background:#fbfcfe;padding:10px}
.qr-box img{width:100%;height:100%;object-fit:contain;display:block}
.qr-ph{font-size:13px;color:var(--text-3);line-height:1.9}
.wechat-id{margin-top:14px;font-size:14px;background:#f1f8f3;color:#0b7a44;border-radius:var(--radius-s);padding:10px 12px;font-weight:700;word-break:break-all}
.modal-acts{display:flex;gap:10px;margin-top:16px}
.modal-acts button{flex:1;padding:11px;border-radius:var(--radius-s);font-weight:700;font-size:14px}
.modal-acts .ok{background:#07c160;color:#fff}
.modal-acts .ok:hover{background:#06a552}
.modal-acts .cancel{background:#f1f5f9;color:#334155}
.modal-tip{font-size:12px;color:var(--text-3);margin-top:12px;line-height:1.7}
.modal-x{position:absolute;right:14px;top:12px;font-size:20px;color:#94a3b8;line-height:1}
.modal-x:hover{color:var(--text-2)}

/* ---------------- 数据加载失败提示 ---------------- */
.load-error{min-height:70vh;display:grid;place-items:center;padding:40px 20px}
.le-card{
  max-width:560px;width:100%;text-align:center;background:#fff;border:1px solid var(--line);
  border-radius:var(--radius);box-shadow:var(--shadow);padding:34px 30px;
}
.le-card h2{font-size:20px;font-weight:800;margin:10px 0 8px}
.le-card p{font-size:14px;color:var(--text-2)}
.le-steps{text-align:left;background:#f8fafd;border-radius:12px;padding:14px 18px;margin:18px 0;font-size:14px;color:var(--text-2)}
.le-steps code{background:#eef3fb;color:var(--blue-d);padding:1px 6px;border-radius:6px;font-size:13px}
.le-err{margin-top:16px;font-size:12px;color:var(--text-3);word-break:break-all}

/* ---------------- 返回顶部 ---------------- */
.to-top{
  position:fixed;right:24px;bottom:86px;z-index:70;width:42px;height:42px;border-radius:50%;
  background:#fff;border:1px solid var(--line);box-shadow:var(--shadow);color:var(--text-2);
  display:none;place-items:center;font-size:18px;
}
.to-top.show{display:grid}
.to-top:hover{color:var(--blue);border-color:#b9d4ff}

/* ---------------- 提示条 ---------------- */
#toast{
  position:fixed;left:50%;bottom:34px;transform:translate(-50%,20px);
  background:#0f2542;color:#fff;padding:12px 22px;border-radius:999px;font-size:14px;
  opacity:0;pointer-events:none;transition:.25s;z-index:99;box-shadow:0 10px 30px rgba(0,0,0,.25);
  max-width:calc(100% - 40px);text-align:center;
}
#toast.show{opacity:1;transform:translate(-50%,0)}

/* ---------------- 页脚 ---------------- */
footer.site{background:#0f2542;color:#9fbde4;padding:34px 0;font-size:13px;margin-top:30px}
footer.site .wrap{display:flex;justify-content:space-between;gap:18px;flex-wrap:wrap}
footer.site b{color:#fff}
footer.site a:hover{color:#fff;text-decoration:underline}

/* ---------------- 手机适配 ---------------- */
@media (max-width:900px){
  .hero h1{font-size:36px}
  .hero{padding:52px 0 58px}
  .about-grid,.new-grid,.entry-grid{grid-template-columns:1fr}
  .board-wrap,.play-grid{grid-template-columns:1fr}
  .sec{padding:40px 0}
  .page-head h1{font-size:24px}
  .logo{font-size:18px}
  nav.main{
    display:none;position:absolute;left:0;right:0;top:66px;background:#fff;
    flex-direction:column;gap:0;padding:8px 16px 14px;border-bottom:1px solid var(--line);
    box-shadow:0 12px 22px rgba(15,37,66,.08);
  }
  nav.main.open{display:flex}
  nav.main a{padding:12px 4px;border-bottom:1px solid #f1f5f9}
  nav.main a.on{border-bottom-color:#f1f5f9}
  .nav-toggle{display:block}
  .top-in{gap:12px}
  .fab{right:14px;bottom:14px;padding:12px 16px;font-size:14px}
  .to-top{right:16px;bottom:74px}
  .lesson-row{gap:12px;padding:12px}
  .lesson-row .dur{font-size:12px}
}
@media (max-width:480px){
  .top-right .btn-admin{display:none}
  .hero-stats{gap:22px}
  .hero-stats b{font-size:20px}
}