/* ============================================================
   工程力学 AI 智慧教学平台 · 共用主题
   深蓝侧边栏 + 卡片式内容区；沿用项目设计令牌语义色
   ============================================================ */
:root{
  /* 平台外壳 */
  --navy-1:#123B63;
  --navy-2:#0C2946;
  --navy-line:rgba(255,255,255,.10);
  --side-on:#1D5C93;
  --side-txt:#C6D8EA;
  /* 语义色（项目设计令牌） */
  --pri:#185FA5; --pri-bg:#E6F1FB;
  --blue:#2B7BD4; --blue-lt:#EAF3FC;
  --ok:#3B6D11; --ok-bg:#EAF3DE;
  --err:#A32D2D; --err-bg:#FCEBEB;
  --amber:#854F0B; --amber-bg:#FAEEDA;
  --purple:#6B4FBB; --purple-bg:#EFEBFA;
  /* 中性 */
  --txt:#2C2C2A; --mut:#6B7480; --line:#E3E8EF;
  --bg:#EEF2F7; --card:#FFFFFF;
  --shadow:0 1px 3px rgba(16,42,67,.06),0 8px 24px rgba(16,42,67,.05);
  --radius:14px;
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{height:100%}
body{
  font-family:"Microsoft YaHei",system-ui,-apple-system,sans-serif;
  background:var(--bg);color:var(--txt);font-size:14px;line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
button{font-family:inherit;cursor:pointer}
a{text-decoration:none;color:inherit}
svg{display:block}

/* ---------------- 外壳布局 ---------------- */
.app{display:flex;flex-direction:column;height:100vh;overflow:hidden}
.topbar{
  flex:0 0 56px;background:linear-gradient(90deg,var(--navy-1),var(--navy-2));
  display:flex;align-items:center;gap:14px;padding:0 18px;color:#fff;z-index:20;
}
.brand{display:flex;align-items:center;gap:10px;font-size:16px;font-weight:600;letter-spacing:.3px}
.brand .logo{
  width:30px;height:30px;border-radius:8px;background:rgba(255,255,255,.14);
  display:flex;align-items:center;justify-content:center;flex:0 0 30px;
}
.brand small{display:block;font-size:11px;font-weight:400;color:#A9C4DE;letter-spacing:0}
.topbar .tagline{
  font-size:12px;color:#A9C4DE;border-left:1px solid var(--navy-line);padding-left:14px;margin-left:2px;
}
.topbar .spacer{flex:1}
.topbar .who{display:flex;align-items:center;gap:8px;font-size:13px;color:#DCE9F5}
.avatar{
  width:28px;height:28px;border-radius:50%;background:#E8F1FB;color:var(--navy-1);
  display:flex;align-items:center;justify-content:center;font-size:12px;font-weight:700;flex:0 0 28px;
}

.body{flex:1;display:flex;min-height:0}

/* ---------------- 侧边栏 ---------------- */
.sidebar{
  flex:0 0 196px;background:linear-gradient(180deg,var(--navy-1),var(--navy-2));
  padding:12px 10px;display:flex;flex-direction:column;gap:3px;overflow-y:auto;
}
.sidebar a{
  display:flex;align-items:center;gap:10px;padding:9px 11px;border-radius:9px;
  color:var(--side-txt);font-size:13.5px;transition:.15s;white-space:nowrap;
}
.sidebar a:hover{background:rgba(255,255,255,.08);color:#fff}
.sidebar a.on{background:var(--side-on);color:#fff;font-weight:600;box-shadow:0 3px 10px rgba(0,0,0,.18)}
.sidebar a svg{flex:0 0 17px;opacity:.92}
.sidebar .grow{flex:1}
.sidebar .foot{font-size:11px;color:#7E9BB8;padding:8px 11px;line-height:1.5}

/* ---------------- 内容区 ---------------- */
.content{flex:1;min-width:0;overflow-y:auto;padding:16px 18px 28px}
.view{display:none}
.view.on{display:block}
.page-title{font-size:16px;font-weight:600;margin-bottom:2px}
.page-sub{font-size:12.5px;color:var(--mut);margin-bottom:14px}

.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px;margin-bottom:14px}
.card>h2{font-size:14.5px;font-weight:600;margin-bottom:10px;display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.card>h2 .more{margin-left:auto;font-size:12px;color:var(--mut);font-weight:400}
.tag{font-size:11px;padding:2px 8px;border-radius:9px;background:var(--pri-bg);color:var(--pri);font-weight:600}
.tag.g{background:var(--ok-bg);color:var(--ok)}
.tag.a{background:var(--amber-bg);color:var(--amber)}
.tag.r{background:var(--err-bg);color:var(--err)}
.tag.p{background:var(--purple-bg);color:var(--purple)}
.mut{color:var(--mut);font-size:12.5px}

/* 统计卡 */
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:14px;margin-bottom:14px}
.stat-card{
  background:#fff;border-radius:var(--radius);box-shadow:var(--shadow);padding:14px 16px;
  display:flex;align-items:center;gap:12px;
}
.stat-card .ico{
  width:42px;height:42px;border-radius:11px;flex:0 0 42px;
  display:flex;align-items:center;justify-content:center;
}
.stat-card .ico.b{background:var(--pri-bg);color:var(--pri)}
.stat-card .ico.g{background:var(--ok-bg);color:var(--ok)}
.stat-card .ico.a{background:#FDF0DC;color:#B3730E}
.stat-card .ico.p{background:var(--purple-bg);color:var(--purple)}
.stat-card .txt b{font-size:21px;font-weight:700;line-height:1.2;display:block}
.stat-card .txt b i{font-size:12px;font-weight:400;color:var(--mut);font-style:normal}
.stat-card .txt span{font-size:12px;color:var(--mut)}
.delta{font-size:11.5px;color:var(--ok);font-weight:600}
.delta.down{color:var(--err)}

/* 两栏/三栏 */
.row{display:grid;gap:14px}
.row.c3{grid-template-columns:repeat(3,minmax(0,1fr))}
.row.c3 .card{min-width:0}
.row.c2{grid-template-columns:1fr 1fr}
@media (max-width:1280px){.stats{grid-template-columns:repeat(2,1fr)}.row.c3{grid-template-columns:1fr}}
@media (max-width:980px){.course .banner{display:none}.topbar .tagline{display:none}}
@media (max-width:820px){.row.c2{grid-template-columns:1fr}}
@media (max-width:640px){.stats{grid-template-columns:1fr}.content{padding:12px 12px 20px}}

/* 当前课程 */
.course{display:flex;gap:16px;align-items:center}
.course .info{flex:1;min-width:0}
.course h2{font-size:16px;font-weight:600;margin-bottom:4px}
.course .meta{font-size:12.5px;color:var(--mut);display:flex;gap:14px;flex-wrap:wrap}
.course .banner{
  flex:0 0 260px;height:66px;border-radius:10px;overflow:hidden;position:relative;
  background:linear-gradient(135deg,#DCEBFA,#EEF5FC);
  display:flex;align-items:center;justify-content:flex-end;padding:0 14px;
}
.course .banner .w1{font-size:13px;color:var(--pri);font-weight:600;text-align:right;line-height:1.7}

/* 案例卡 */
.case-head{display:flex;gap:13px}
.case-thumb{
  flex:0 0 168px;height:104px;border-radius:10px;position:relative;overflow:hidden;
  background:linear-gradient(160deg,#CFE3F6,#EAF3FC);
  display:flex;align-items:center;justify-content:center;
}
.case-thumb .play{
  width:38px;height:38px;border-radius:50%;background:rgba(255,255,255,.92);color:var(--pri);
  display:flex;align-items:center;justify-content:center;box-shadow:0 3px 10px rgba(0,0,0,.16);
}
.case-body{flex:1;min-width:0}
.case-body h3{font-size:14.5px;font-weight:600;margin-bottom:6px}
.case-body .tags{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:7px}
.case-body p{font-size:12.5px;color:var(--mut)}
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:6px;
  padding:7px 14px;border:none;border-radius:9px;background:var(--blue);color:#fff;
  font-size:13px;font-weight:500;transition:.15s;
}
.btn:hover{filter:brightness(1.06)}
.btn.ghost{background:#fff;color:var(--pri);border:1.5px solid var(--pri)}
.btn.sm{padding:5px 11px;font-size:12.5px}
.btn.blk{width:100%}
.btn:disabled{background:#C9D2DC;cursor:not-allowed;filter:none}

/* 二维码 */
.qr-wrap{display:flex;flex-direction:column;align-items:center;gap:10px}
.qr-box{
  width:158px;height:158px;background:#fff;border:1px solid var(--line);border-radius:12px;
  padding:8px;display:flex;align-items:center;justify-content:center;
}
.qr-box svg,.qr-box img{width:100%;height:100%}
.qr-status{display:flex;align-items:center;gap:6px;font-size:13px;font-weight:600}
#qrUrl{word-break:break-all;max-width:100%;font-size:11.5px;line-height:1.45}
.dot{width:8px;height:8px;border-radius:50%;background:var(--ok);box-shadow:0 0 0 4px var(--ok-bg)}
.dot.off{background:#B9C2CC;box-shadow:0 0 0 4px #EEF1F5}

/* 实时数据环形 */
.rings{display:grid;grid-template-columns:repeat(auto-fit,minmax(70px,1fr));gap:8px;margin-top:12px;text-align:center}
.ring{position:relative}
.ring svg{width:74px;height:74px;margin:0 auto}
.ring .val{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;font-size:14px;font-weight:700}
.ring .cap{font-size:11.5px;color:var(--mut);margin-top:2px}

/* 列表条 */
.bar-row{margin:9px 0}
.bar-row .top{display:flex;justify-content:space-between;font-size:12.5px;margin-bottom:4px}
.bar{height:9px;background:#EEF1F5;border-radius:6px;overflow:hidden}
.bar i{display:block;height:100%;border-radius:6px;background:var(--err);transition:width .4s}
.bar i.b{background:var(--blue)}.bar i.g{background:var(--ok)}.bar i.a{background:#E0A32E}

/* 表格 */
table{width:100%;border-collapse:collapse;font-size:13px}
th,td{padding:8px 9px;text-align:center;border-bottom:1px solid var(--line)}
th{font-size:12px;color:var(--mut);font-weight:600;background:#FAFBFD}
td.l{text-align:left}
tbody tr:hover{background:#FAFCFE}

/* 网格卡片（案例库/题库） */
.tiles{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:14px}
.tile{background:#fff;border-radius:var(--radius);box-shadow:var(--shadow);overflow:hidden;transition:.18s;cursor:pointer}
.tile:hover{transform:translateY(-2px);box-shadow:0 6px 20px rgba(16,42,67,.12)}
.tile .ph{height:112px;background:linear-gradient(160deg,#D3E5F7,#EDF5FC);display:flex;align-items:center;justify-content:center;color:var(--pri)}
.tile .bd{padding:11px 13px}
.tile .bd h4{font-size:13.5px;font-weight:600;margin-bottom:4px}
.tile .bd p{font-size:12px;color:var(--mut)}

.placeholder{
  border:1.5px dashed var(--line);border-radius:12px;padding:22px;text-align:center;color:var(--mut);font-size:13px;
}
.errbox{background:var(--err-bg);color:var(--err);border-radius:9px;padding:9px 12px;font-size:12.5px;margin-bottom:12px;display:none}
.notice{font-size:12px;color:var(--mut);background:#FAFBFD;border-radius:9px;padding:9px 12px;margin-top:10px}

/* 移动端学生页用 */
body.mobile{background:#EFF3F8}
.phone{max-width:430px;margin:0 auto;min-height:100vh;background:#F4F7FB;padding-bottom:64px;position:relative}
.m-head{background:linear-gradient(135deg,#1B5FA5,#2B7BD4);color:#fff;padding:14px 16px 46px;border-radius:0 0 20px 20px}
.m-head .row1{display:flex;align-items:center;justify-content:space-between;font-size:14px;font-weight:600}
.m-user{display:flex;align-items:center;gap:10px;margin-top:14px}
.m-user .av{width:44px;height:44px;border-radius:50%;background:rgba(255,255,255,.22);display:flex;align-items:center;justify-content:center;font-size:16px;font-weight:700}
.m-user .nm b{font-size:15px;display:block}
.m-user .nm span{font-size:11.5px;color:#CFE2F6}
.m-body{padding:0 14px;margin-top:-32px}
.m-card{background:#fff;border-radius:14px;box-shadow:var(--shadow);padding:14px;margin-bottom:12px}
.m-grid4{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.m-quick{background:#fff;border-radius:14px;padding:14px 8px;text-align:center;box-shadow:var(--shadow);cursor:pointer}
.m-quick .ci{width:40px;height:40px;border-radius:12px;margin:0 auto 7px;display:flex;align-items:center;justify-content:center}
.m-quick span{font-size:11.5px}
.m-nav{position:fixed;bottom:0;left:0;right:0;max-width:430px;margin:0 auto;background:#fff;border-top:1px solid var(--line);display:flex;z-index:30}
.m-nav button{flex:1;border:none;background:none;padding:8px 0 7px;font-size:11px;color:var(--mut);display:flex;flex-direction:column;align-items:center;gap:2px}
.m-nav button.on{color:var(--pri);font-weight:600}
.step{display:flex;align-items:center;gap:8px;font-size:12.5px;color:var(--mut);margin-bottom:12px}
.step b{width:20px;height:20px;border-radius:50%;background:var(--pri-bg);color:var(--pri);display:flex;align-items:center;justify-content:center;font-size:11px}
.opt{display:block;border:1.5px solid var(--line);border-radius:11px;padding:11px 12px;margin:8px 0;font-size:13.5px;cursor:pointer;transition:.15s}
.opt.sel{border-color:var(--pri);background:var(--pri-bg)}
.opt.ok{border-color:var(--ok);background:var(--ok-bg)}
.opt.no{border-color:var(--err);background:var(--err-bg)}
input[type=text]{width:100%;padding:9px 11px;border:1px solid var(--line);border-radius:10px;font-size:14px;font-family:inherit;color:var(--txt)}
.prog{height:6px;background:#E9EDF3;border-radius:6px;overflow:hidden;margin:8px 0}
.prog i{display:block;height:100%;background:var(--blue);transition:width .3s}