:root{
  --bg:#f4f6fb; --panel:#ffffff; --ink:#1f2430; --muted:#6b7280;
  --line:#e6e9f0; --primary:#4f46e5; --primary-d:#4338ca; --primary-l:#eef2ff;
  --ok:#16a34a; --warn:#d97706; --bad:#dc2626;
  --shadow:0 1px 3px rgba(16,24,40,.06),0 6px 20px rgba(16,24,40,.05);
  --radius:14px;
}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  background:var(--bg);color:var(--ink);font-size:14px;line-height:1.6}
a{color:var(--primary)}
h1,h2,h3{margin:0 0 .4em;font-weight:700}
.muted{color:var(--muted)}
.sm{font-size:12px}

/* 顶部栏 */
.topbar{height:56px;background:var(--panel);border-bottom:1px solid var(--line);
  display:flex;align-items:center;justify-content:space-between;padding:0 20px;position:sticky;top:0;z-index:10}
.brand{display:flex;align-items:center;gap:8px;font-weight:700;font-size:15px}
.logo{display:inline-flex;width:28px;height:28px;border-radius:8px;background:var(--primary);color:#fff;
  align-items:center;justify-content:center;font-size:16px}
.topbar-right{display:flex;align-items:center;gap:12px}
.user-tag{background:var(--primary-l);color:var(--primary-d);padding:4px 10px;border-radius:999px;font-size:12px;font-weight:600}

/* 布局 */
.layout{display:flex;min-height:calc(100vh - 56px)}
.sidebar{width:200px;background:var(--panel);border-right:1px solid var(--line);padding:16px 12px;display:flex;flex-direction:column;gap:6px}
.nav-item,.nav-ext{text-align:left;border:none;background:transparent;padding:11px 14px;border-radius:10px;cursor:pointer;
  color:var(--muted);font-size:14px;font-weight:600;transition:.15s}
.nav-item:hover,.nav-ext:hover{background:var(--bg);color:var(--ink)}
.nav-item.active,.nav-ext.active{background:var(--primary-l);color:var(--primary-d)}
.content{flex:1;padding:24px 28px;max-width:1200px}
.view{display:none}
.view.active{display:block;animation:fade .25s ease}
@keyframes fade{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}
.page-head{margin-bottom:18px}
.page-head h2{font-size:22px}

/* 卡片 */
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px;box-shadow:var(--shadow)}
.stat-cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px;margin-bottom:20px}
.stat{text-align:center;padding:18px}
.stat-v{font-size:26px;font-weight:800;color:var(--primary-d)}
.stat-k{color:var(--muted);font-size:13px;margin-top:2px}

/* 按钮 */
.btn-primary{background:var(--primary);color:#fff;border:none;padding:10px 18px;border-radius:10px;font-weight:600;cursor:pointer;font-size:14px;transition:.15s}
.btn-primary:hover{background:var(--primary-d)}
.btn-primary.sm,.btn-ghost.sm{padding:6px 12px;font-size:13px}
.btn-ghost{background:transparent;border:1px solid var(--line);color:var(--muted);padding:10px 16px;border-radius:10px;cursor:pointer;font-weight:600;font-size:13px}
.btn-ghost:hover{border-color:var(--primary);color:var(--primary)}

/* 标签 */
.tag{display:inline-block;padding:2px 9px;border-radius:999px;font-size:11px;font-weight:700}
.tag-easy{background:#dcfce7;color:#15803d}
.tag-mid{background:#fef9c3;color:#a16207}
.tag-hard{background:#fee2e2;color:#b91c1c}

/* 任务网格 */
.task-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:16px}
.task-card{cursor:pointer;transition:.18s;display:flex;flex-direction:column;gap:8px}
.task-card:hover{transform:translateY(-3px);box-shadow:0 10px 30px rgba(16,24,40,.1)}
.task-top{display:flex;justify-content:space-between;align-items:center}
.task-foot{display:flex;justify-content:space-between;align-items:center;margin-top:auto}
.status-pill{padding:3px 10px;border-radius:999px;font-size:12px;font-weight:700}
.st-todo{color:var(--muted)} .task-card.st-todo{border-top:3px solid #cbd5e1}
.st-wait{color:var(--warn);background:#fffbeb} .task-card.st-wait{border-top:3px solid var(--warn)}
.st-done{color:var(--ok);background:#f0fdf4} .task-card.st-done{border-top:3px solid var(--ok)}
.arrow{color:var(--primary);font-weight:800}

/* 任务详情 / 编辑 */
.task-desc{background:var(--bg);border-radius:10px;padding:12px 14px;margin:10px 0;font-size:13.5px}
.req-box{background:var(--primary-l);border-radius:10px;padding:12px 14px;font-size:13px}
.req-box ul{margin:6px 0 0;padding-left:18px}
.graded-box{background:#f0fdf4;border:1px solid #bbf7d0;border-radius:10px;padding:12px 14px;margin-top:10px;font-size:13px}

.editor-layout{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:14px}
.editor-pane,.preview-pane{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;display:flex;flex-direction:column}
.pane-head{display:flex;justify-content:space-between;align-items:center;padding:10px 14px;background:#fafbff;border-bottom:1px solid var(--line);font-size:13px;font-weight:600;color:var(--muted)}
#codeArea{width:100%;min-height:340px;border:none;padding:14px;font-family:"SFMono-Regular",Consolas,Menlo,monospace;font-size:13px;resize:vertical;outline:none;line-height:1.55;color:#0f172a;background:#fcfdff}
#preview{width:100%;min-height:420px;border:none;background:#fff}
.auto-check{margin-top:14px;background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:14px}
.check-result{margin-top:8px;font-size:13px}
.check-row{padding:3px 0}
.check-row.ok{color:var(--ok)} .check-row.no{color:var(--bad)}
.submit-row{display:flex;align-items:center;gap:14px;margin-top:14px}

/* 表格 */
.tbl{width:100%;border-collapse:collapse;font-size:13.5px}
.tbl th,.tbl td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line)}
.tbl th{background:#fafbff;color:var(--muted);font-weight:700;position:sticky;top:0}
.tbl tbody tr:hover{background:var(--bg)}
.select{width:100%;padding:9px 12px;border:1px solid var(--line);border-radius:9px;font-size:14px;background:#fff;margin:8px 0 12px}
.fb{width:100%;min-height:90px;border:1px solid var(--line);border-radius:9px;padding:10px;font-family:inherit;font-size:13px;resize:vertical;outline:none}

/* 批改 */
.grade-layout{display:grid;grid-template-columns:300px 1fr;gap:16px;align-items:start}
.sub-list{margin-top:8px;display:flex;flex-direction:column;gap:8px;max-height:70vh;overflow:auto}
.sub-item{padding:10px 12px;border:1px solid var(--line);border-radius:10px;cursor:pointer;transition:.15s}
.sub-item:hover{background:var(--bg)}
.sub-item.sel{border-color:var(--primary);background:var(--primary-l)}
.sub-item.st-done{border-left:3px solid var(--ok)}
.sub-item.st-wait{border-left:3px solid var(--warn)}
.grade-head{margin-bottom:10px}
#stuCode{width:100%;min-height:260px;border:1px solid var(--line);border-radius:9px;padding:12px;font-family:"SFMono-Regular",Consolas,monospace;font-size:12.5px;background:#fcfdff;color:#0f172a;resize:vertical;outline:none}
.grade-detail-pane{min-height:300px}

/* 概览条形 */
.bar-row{display:flex;align-items:center;gap:12px;margin:10px 0;font-size:13px}
.bar-label{width:140px;flex:none;color:var(--ink);font-weight:600}
.bar-track{flex:1;height:12px;background:var(--bg);border-radius:999px;overflow:hidden}
.bar-fill{height:100%;background:linear-gradient(90deg,var(--primary),#818cf8);border-radius:999px}
.bar-num{width:160px;flex:none;text-align:right;color:var(--muted)}

/* 登录页 */
.auth-page{display:flex;align-items:center;justify-content:center;min-height:100vh;background:linear-gradient(135deg,#eef2ff,#f4f6fb)}
.auth-wrap{display:grid;grid-template-columns:1.1fr 1fr;max-width:920px;width:92%;background:var(--panel);border-radius:20px;overflow:hidden;box-shadow:0 20px 60px rgba(16,24,40,.12)}
.auth-hero{background:linear-gradient(160deg,var(--primary),#7c3aed);color:#fff;padding:42px 38px;display:flex;flex-direction:column;justify-content:center}
.auth-hero .brand{color:#fff;font-size:16px;margin-bottom:18px}
.auth-hero .logo{background:rgba(255,255,255,.2)}
.auth-hero h1{font-size:30px;line-height:1.25;margin-bottom:14px}
.hero-sub{opacity:.92;font-size:14px;max-width:360px}
.hero-points{list-style:none;padding:0;margin:18px 0 0;font-size:13.5px;opacity:.95}
.hero-points li{margin:8px 0}
.auth-card{padding:42px 38px;display:flex;flex-direction:column;justify-content:center}
.role-tabs{display:flex;background:var(--bg);border-radius:10px;padding:4px;margin-bottom:20px}
.role-tab{flex:1;border:none;background:transparent;padding:9px;border-radius:8px;cursor:pointer;font-weight:600;color:var(--muted)}
.role-tab.active{background:#fff;color:var(--primary-d);box-shadow:var(--shadow)}
.auth-form{display:none;flex-direction:column;gap:14px}
.auth-form.active{display:flex}
.auth-form label{display:flex;flex-direction:column;gap:6px;font-size:13px;font-weight:600;color:var(--ink)}
.auth-form input{padding:11px 13px;border:1px solid var(--line);border-radius:10px;font-size:14px;outline:none}
.auth-form input:focus{border-color:var(--primary)}
.hint{font-size:12px;color:var(--muted);background:var(--bg);padding:10px 12px;border-radius:9px}

@media(max-width:860px){
  .auth-wrap{grid-template-columns:1fr}
  .auth-hero{display:none}
  .editor-layout,.grade-layout{grid-template-columns:1fr}
  .sidebar{width:140px}
  .content{padding:16px}
}

/* 学习辅助区：笔记 / 题解 / 答疑 / 评测 */
.assist-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-top:16px}
.assist{display:flex;flex-direction:column}
.assist .fb{min-height:120px;resize:vertical}
.sol-box{font-size:13px;line-height:1.7;white-space:pre-wrap}
.sol-points{margin-bottom:8px}
.sol-points ul{margin:6px 0 0;padding-left:18px}
.sol-code{background:#0f172a;color:#e2e8f0;padding:12px;border-radius:10px;overflow:auto;font-size:12.5px;line-height:1.5;white-space:pre-wrap;word-break:break-all}
.qa-list{display:flex;flex-direction:column;gap:10px;max-height:220px;overflow:auto}
.qa-item{border:1px solid var(--line);border-radius:10px;padding:10px 12px;background:var(--bg)}
.qa-q{font-size:13px}
.qa-a{margin-top:6px;font-size:13px;color:var(--primary-d);background:var(--primary-l);padding:6px 10px;border-radius:8px}
.qa-ask{display:flex;gap:8px;margin-top:10px}
.qa-ask .select{flex:1}
.qa-answer{display:flex;gap:8px;margin-top:6px}
.qa-answer .select{flex:1}
.eval-report{margin-top:12px;background:var(--primary-l);color:var(--primary-d);border-radius:10px;padding:10px 14px;font-size:13px;font-weight:600}
.warn{color:var(--bad)}
.warn-box{background:#fef2f2;color:var(--bad);border:1px solid #fecaca;border-radius:10px;padding:10px 14px;font-size:13px;margin-bottom:12px}
.sol-toggle{display:flex;align-items:center;justify-content:space-between;margin:8px 0;gap:8px}
.btn.on{background:var(--ok);border-color:var(--ok);color:#fff}
@media(max-width:860px){.assist-grid{grid-template-columns:1fr}}