:root{
  --bg:#f5f7fa; --panel:#ffffff; --ink:#1f2937; --muted:#6b7280;
  --line:#e5e7eb; --primary:#2f6fed; --primary-d:#1e4fb0;
  scroll-behavior:smooth;
  --ok:#16a34a; --warn:#d97706; --lock:#9ca3af; --danger:#dc2626;
  --chip:#eef3ff; --shadow:0 1px 3px rgba(0,0,0,.08),0 1px 2px rgba(0,0,0,.04);
  --radius:12px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
html{overflow-x:hidden}
body{
  font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",Segoe UI,Roboto,sans-serif;
  background:var(--bg); color:var(--ink); font-size:15px; line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
.topbar{
  position:sticky; top:0; z-index:20; display:flex; align-items:center; justify-content:space-between;
  padding:10px 16px; background:linear-gradient(90deg,#1e3a8a,#2f6fed); color:#fff; box-shadow:var(--shadow);
}
.brand{display:flex; align-items:center; gap:10px}
.logo{width:36px;height:36px;border-radius:9px;background:rgba(255,255,255,.18);display:flex;align-items:center;justify-content:center;font-size:22px;font-weight:700}
.brand-title{font-weight:700;font-size:16px;line-height:1.1}
.brand-sub{font-size:11px;opacity:.82}
.nav{display:flex;gap:6px;align-items:center}
.nav-link{color:#fff;text-decoration:none;font-size:13px;padding:6px 10px;border-radius:8px;opacity:.9;position:relative}
.nav-link.active{background:rgba(255,255,255,.2);opacity:1;font-weight:600}
.badge{position:absolute;top:-4px;right:-6px;background:var(--danger);color:#fff;font-size:10px;border-radius:10px;padding:0 5px;min-width:16px;text-align:center;display:none}
.badge.show{display:inline-block}
.view{max-width:920px;margin:0 auto;padding:16px}
.footpad{height:24px}

/* 卡片与通用 */
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:14px 16px;box-shadow:var(--shadow);margin-bottom:14px}
h2.section{font-size:18px;margin:4px 0 12px}
h3{font-size:15px;margin:14px 0 6px}
.muted{color:var(--muted);font-size:13px}
.btn{display:inline-flex;align-items:center;gap:6px;border:none;border-radius:9px;padding:9px 14px;font-size:14px;cursor:pointer;background:var(--primary);color:#fff;font-weight:600;transition:.15s}
.btn:hover{background:var(--primary-d)}
.btn.ghost{background:#fff;color:var(--primary);border:1px solid var(--primary)}
.btn.soft{background:var(--chip);color:var(--primary-d)}
.btn:disabled{opacity:.5;cursor:not-allowed}
.btn.sm{padding:6px 10px;font-size:13px}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.spacer{flex:1}
.tag{display:inline-block;font-size:12px;padding:2px 8px;border-radius:20px;background:var(--chip);color:var(--primary-d);margin-right:6px}
.tag.g{background:#e7f6ee;color:var(--ok)}
.tag.w{background:#fdf0e3;color:var(--warn)}
.tag.l{background:#f1f3f5;color:var(--lock)}

/* 路径树 */
.tree{display:flex;flex-direction:column;gap:10px}
.node{display:flex;gap:12px;align-items:flex-start;background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:12px 14px;box-shadow:var(--shadow);position:relative}
.node.locked{opacity:.72;background:#fafafa}
.node.mastered{border-color:#bfe6cc}
/* 返回路径后，定位到的技巧节点高亮一下 */
@keyframes nodeFlash{0%{box-shadow:0 0 0 3px var(--primary);border-color:var(--primary)}100%{box-shadow:var(--shadow);border-color:var(--line)}}
.node.flash{animation:nodeFlash 1.8s ease-out}
.node .step{width:30px;height:30px;border-radius:50%;flex:0 0 auto;display:flex;align-items:center;justify-content:center;font-weight:700;color:#fff;background:var(--primary)}
.node.locked .step{background:var(--lock)}
.node.mastered .step{background:var(--ok)}
.node .body{flex:1;min-width:0}
.node .title{font-weight:700;font-size:16px;display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.node .meta{font-size:12px;color:var(--muted);margin-top:2px}
.node .acts{margin-top:8px}
.status-pill{font-size:12px;padding:2px 9px;border-radius:20px}
.status-pill.lock{background:#f1f3f5;color:var(--lock)}
.status-pill.learn{background:var(--chip);color:var(--primary-d)}
.status-pill.done{background:#e7f6ee;color:var(--ok)}
.lock-ico{font-size:14px}
.grade-sep{margin:18px 0 6px;font-weight:700;color:var(--primary-d);font-size:14px;border-left:4px solid var(--primary);padding-left:8px}
.stage-banner{display:flex;align-items:baseline;gap:10px;margin:22px 0 4px;padding:10px 14px;border-radius:10px;background:linear-gradient(90deg,#1e3a8a,#2f6fed);color:#fff;box-shadow:var(--shadow)}
.stage-banner.sm{margin:16px 0 2px;padding:6px 12px;background:#eef3ff}
.stage-name{font-weight:800;font-size:17px}
.stage-banner.sm .stage-name{font-size:15px;color:var(--primary-d)}
.stage-desc{font-size:12px;opacity:.85}
.stage-banner.sm .stage-desc{display:none}
.grade-tag{font-weight:700;color:var(--primary-d);font-size:14px}
.grade-count{font-size:12px;color:var(--muted);font-weight:400;margin-left:8px}

/* 学习页 */
.tech-head{display:flex;align-items:center;gap:10px;flex-wrap:wrap;margin-bottom:6px}
.kou{background:#fff8ec;border:1px dashed var(--warn);border-radius:10px;padding:10px 12px;color:#8a5a00;font-size:14px;margin:10px 0}
.kou b{color:var(--warn)}
.steps{counter-reset:s;list-style:none;padding:0;margin:8px 0}
.steps li{position:relative;padding:8px 8px 8px 38px;border-bottom:1px dashed var(--line)}
.steps li:before{counter-increment:s;content:counter(s);position:absolute;left:6px;top:8px;width:22px;height:22px;border-radius:50%;background:var(--chip);color:var(--primary-d);font-weight:700;display:flex;align-items:center;justify-content:center;font-size:13px}
.anim-wrap{background:#0f172a;border-radius:12px;padding:8px;margin:12px 0;position:relative;overflow:hidden}
.anim-wrap svg{width:100%;height:auto;display:block}
.anim-cap{color:#cbd5e1;font-size:12px;padding:6px 8px 2px}
.anim-ctrls{display:flex;gap:8px;flex-wrap:wrap;padding:6px 8px 10px}
.anim-ctrls .btn{background:#1e293b;color:#e2e8f0}
.anim-ctrls .btn:hover{background:#334155}

/* 练习 */
.q{background:#fff;border:1px solid var(--line);border-radius:12px;padding:14px;margin-bottom:12px}
.q .qtext{font-size:15px;font-weight:600;margin-bottom:10px}
.opts{display:flex;flex-direction:column;gap:8px}
.opt{display:flex;gap:10px;align-items:center;border:1px solid var(--line);border-radius:9px;padding:9px 12px;cursor:pointer;transition:.12s}
.opt:hover{border-color:var(--primary)}
.opt.sel{border-color:var(--primary);background:var(--chip)}
.opt.correct{border-color:var(--ok);background:#e7f6ee}
.opt.wrong{border-color:var(--danger);background:#fdeaea}
.opt .mark{width:22px;height:22px;border-radius:50%;border:1px solid var(--line);flex:0 0 auto;display:flex;align-items:center;justify-content:center;font-size:12px;color:var(--muted)}
.opt.correct .mark{background:var(--ok);color:#fff;border-color:var(--ok)}
.opt.wrong .mark{background:var(--danger);color:#fff;border-color:var(--danger)}
.explain{background:#f8fafc;border-left:3px solid var(--primary);padding:8px 12px;margin-top:10px;font-size:13px;border-radius:0 8px 8px 0}
/* 判断题专用样式：✓ 对 / ✗ 错 并排两个大按钮，对绿错红 */
.opts.judge{flex-direction:row;gap:10px}
.opt.judge{flex:1;justify-content:center;font-weight:600;font-size:15px}
.opt.judge .mark.judge{width:26px;height:26px;font-size:16px;border:none}
.opt.judge:nth-child(1) .mark.judge{background:var(--ok);color:#fff}
.opt.judge:nth-child(2) .mark.judge{background:var(--danger);color:#fff}
.qfig{background:#fbfdff;border:1px solid var(--line);border-radius:10px;padding:8px;margin:2px 0 12px;text-align:center}
.qfig svg{margin:0 auto}
.qres{font-weight:700;margin:6px 0}
/* 薄弱点复习：进度与即时反馈 */
.rev-prog{font-size:13px;color:var(--muted);margin:4px 0 10px}
.rev-prog b{color:var(--ink);font-size:15px}
.rev-note{margin-top:8px;font-size:13px;font-weight:700;padding:6px 10px;border-radius:8px}
.rev-note.ok{background:#eafaf0;color:var(--ok)}
.rev-note.bad{background:#fdeeee;color:var(--danger)}
.q.cleared{border-color:#bfe9cd;background:#f6fdf8}

/* 进度 */
.stat-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:10px;margin-bottom:14px}
.stat{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:12px;text-align:center}
.stat .n{font-size:24px;font-weight:800;color:var(--primary)}
.stat .l{font-size:12px;color:var(--muted)}
.bar{height:8px;border-radius:6px;background:#eee;overflow:hidden;margin-top:6px}
.bar > i{display:block;height:100%;background:var(--ok)}
.empty{text-align:center;color:var(--muted);padding:30px 10px}
.center{text-align:center}
.toast{position:fixed;left:50%;bottom:30px;transform:translateX(-50%) translateY(20px);background:#1f2937;color:#fff;padding:10px 18px;border-radius:24px;font-size:14px;opacity:0;pointer-events:none;transition:.25s;z-index:50}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
.hint{font-size:13px;color:var(--muted);background:#f8fafc;border:1px solid var(--line);border-radius:8px;padding:8px 12px;margin:8px 0}

/* 相关项目推荐 */
.res-cat{margin:0 0 6px;font-size:16px;color:var(--primary-d)}
.res-desc{font-size:13px;color:var(--muted);margin-bottom:12px}
.res-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:12px}
.res-item{display:block;text-decoration:none;background:#fbfdff;border:1px solid var(--line);border-radius:10px;padding:12px;transition:.12s}
.res-item:hover{border-color:var(--primary);box-shadow:var(--shadow)}
.res-head{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap;margin-bottom:6px}
.res-name{font-weight:700;font-size:15px;color:var(--ink)}
.res-tags{display:flex;gap:5px;flex-wrap:wrap}
.res-tag{font-size:11px;padding:2px 7px;border-radius:20px;background:#eef3ff;color:var(--primary-d)}
.res-summary{font-size:13px;color:var(--ink);margin-bottom:8px;line-height:1.5}
.res-why{font-size:12px;color:var(--muted);line-height:1.5}
.res-why b{color:var(--warn)}
.res-url{font-size:11px;color:var(--primary);margin-top:8px;word-break:break-all}

@media(max-width:560px){
  .brand-sub{display:none}
  .nav-link{font-size:12px;padding:6px 7px;flex:0 0 auto}
  .view{padding:12px}
  .topbar{flex-wrap:wrap;padding:8px 12px}
  .brand{margin-right:auto}
  .nav{width:100%;justify-content:flex-start;gap:4px;overflow-x:auto;-webkit-overflow-scrolling:touch}
  .nav::-webkit-scrollbar{display:none}
}

/* 学习路径：侧边栏（学段 → 年级 两级） + 主区 */
.view.path-view{max-width:1200px}
.path-layout{display:flex;gap:16px;align-items:flex-start}
.path-main{flex:1;min-width:0}
.sidebar{width:218px;flex:0 0 218px;position:sticky;top:72px;align-self:flex-start;max-height:calc(100vh - 92px);overflow:auto;background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:10px;box-shadow:var(--shadow)}
.sb-head{display:flex;align-items:center;justify-content:space-between;padding:2px 4px 8px;border-bottom:1px solid var(--line);margin-bottom:6px}
.sb-title{font-weight:700;font-size:13px;color:var(--primary-d)}
.sb-toggle{border:1px solid var(--line);background:#fff;border-radius:8px;width:26px;height:24px;cursor:pointer;color:var(--muted);font-size:13px;line-height:1}
.sb-toggle:hover{background:var(--chip)}
.sb-item{display:flex;align-items:center;gap:6px;padding:7px 10px;border-radius:8px;color:var(--ink);text-decoration:none;font-size:13px;margin-bottom:4px}
.sb-item:hover{background:var(--chip)}
.sb-item.active{background:var(--primary);color:#fff;font-weight:600}
.sb-stage{margin:4px 0}
.sb-stage-h{display:flex;align-items:center;gap:6px;padding:7px 8px;border-radius:8px;cursor:pointer;font-weight:700;font-size:14px;color:var(--primary-d);background:#f3f6fc;user-select:none}
.sb-stage-h:hover{background:#e8eefb}
.sb-caret{font-size:11px;color:var(--muted)}
.sb-cnt{margin-left:auto;font-size:11px;font-weight:400;color:var(--muted);background:#fff;border:1px solid var(--line);border-radius:10px;padding:0 6px}
.sb-grades{display:none;padding:4px 0 6px 6px;border-left:2px solid var(--line);margin:4px 0 4px 8px}
.sb-stage.open .sb-grades{display:block}
.sb-grade{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:6px 10px;border-radius:7px;color:var(--ink);text-decoration:none;font-size:13px;margin:2px 0}
.sb-grade:hover{background:var(--chip)}
.sb-grade.active{background:var(--primary);color:#fff;font-weight:600}
.sb-grade.active .sb-cnt{color:#fff;background:rgba(255,255,255,.22);border-color:transparent}
.path-layout.sb-collapsed .sidebar{display:none}
.sb-fab{display:none}
.sb-top-btn{display:none;align-items:center;gap:6px;margin:0 0 10px;background:var(--chip);color:var(--primary-d);border:1px solid var(--primary);border-radius:9px;padding:8px 12px;font-size:13px;font-weight:600;cursor:pointer}
.sb-top-btn:hover{background:#e6edff}
.sb-mask{display:none;position:fixed;inset:0;z-index:39}
@media (max-width:820px){
  .view.path-view{max-width:100%}
  .sidebar{position:fixed;top:0;left:0;bottom:0;width:240px;max-height:none;border-radius:0;transform:translateX(-100%);transition:transform .2s ease;z-index:40;padding-top:14px}
  .path-layout.sb-drawer-open .sidebar{transform:translateX(0)}
  .path-layout.sb-drawer-open .sb-mask{visibility:visible}
  .sb-toggle{display:none}
  .sb-top-btn{display:inline-flex}
  .sb-mask{display:block;visibility:hidden}
  .sb-fab{display:inline-flex;align-items:center;gap:6px;position:fixed;left:10px;bottom:14px;z-index:41;background:var(--primary);color:#fff;border:none;border-radius:22px;padding:9px 14px;font-size:13px;font-weight:600;cursor:pointer;box-shadow:var(--shadow)}
}

/* ===== 去学习 · 典型例题 ===== */
.ex-list{display:flex;flex-direction:column;gap:14px;margin-top:6px}
.ex{border:1px solid var(--line);border-radius:12px;padding:12px 14px;background:var(--panel)}
.ex-q{font-size:15px;font-weight:600;color:var(--ink);line-height:1.5;margin-bottom:8px;display:flex;align-items:flex-start;gap:8px}
.ex-no{flex:0 0 auto;min-width:26px;height:26px;line-height:26px;text-align:center;background:#eef3ff;color:var(--primary);border-radius:7px;font-size:13px;font-weight:700}
.ex-opts{display:flex;flex-wrap:wrap;gap:8px}
.ex-opt{display:inline-flex;align-items:center;padding:6px 12px;border:1px solid var(--line);border-radius:9px;background:#f8fafc;font-size:14px;color:var(--ink)}
.ex-opt.correct{border-color:var(--ok);background:#eafaf0;color:#15803d;font-weight:700}
.ex-why{margin-top:10px;border-top:1px dashed var(--line);padding-top:8px}
.ex-why summary{cursor:pointer;color:var(--primary);font-size:13px;font-weight:600;user-select:none;list-style:none;outline:none}
.ex-why summary::-webkit-details-marker{display:none}
.ex-why summary::before{content:"▸ ";color:var(--primary)}
.ex-why[open] summary::before{content:"▾ "}
.ex-exp{margin-top:8px;font-size:14px;color:var(--ink);line-height:1.6;background:#f8fafc;border-radius:8px;padding:8px 10px}
.ex-point{margin-top:6px;font-size:13px;color:var(--warn)}
.hint-inline{font-size:12px;color:var(--muted);font-weight:400}

/* ===== AI 知识漏洞诊断 ===== */
.diag-head .diag-top{display:flex;gap:16px;align-items:center;flex-wrap:wrap}
.diag-mastery{flex:0 0 auto;text-align:center;background:linear-gradient(135deg,#eef3ff,#e6edff);border-radius:14px;padding:10px 16px}
.diag-mastery .n{font-size:30px;font-weight:800;color:var(--primary);line-height:1.1}
.diag-mastery .l{font-size:12px;color:var(--muted)}
.diag-stats{flex:1 1 auto;display:grid;grid-template-columns:repeat(2,1fr);gap:6px 14px;font-size:13px;color:var(--ink)}
.diag-stats b{color:var(--primary);font-size:16px;margin-right:3px}
.diag-head .bar{margin-top:12px;height:9px}
.stage-row{display:flex;align-items:center;gap:10px;margin:8px 0}
.stage-row .stage-name{flex:0 0 52px;font-weight:700;font-size:13px;color:var(--ink)}
.stage-row .bar.mini{flex:1 1 auto;height:8px;margin:0}
.stage-row .bar.mini i.warn{background:var(--warn)}
.stage-row .stage-num{flex:0 0 auto;font-size:12px;color:var(--muted)}
.diag-concl{background:linear-gradient(135deg,#fffaf0,#fff7e6);border-color:#ffe1a8}
.diag-concl h3{margin-top:0}
.diag-concl .muted{line-height:1.7;font-size:14px}
.diag-concl b{color:#b45309}
.diag-list{display:flex;flex-direction:column;gap:8px;margin-top:4px}
.diag-item{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:10px 12px;border:1px solid var(--line);border-radius:11px;background:var(--panel)}
.diag-item .di-main{flex:1 1 auto;min-width:0}
.diag-item .di-name{font-size:14px;font-weight:700;color:var(--ink)}
.diag-item .di-meta{font-size:12px;color:var(--muted);margin-top:2px}
.tag.ok{background:#eafaf0;color:#15803d;border-color:#b7ebc6}
.tag.warn{background:#fff5e6;color:#b45309;border-color:#ffd79a}
.tag.bad{background:#fdecec;color:#c0392b;border-color:#f5b5b0}
@media (max-width:560px){
  .diag-stats{grid-template-columns:repeat(2,1fr)}
  .diag-mastery .n{font-size:26px}
}