: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}
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}

/* 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}
  .view{padding:12px}
}