/* ===== 基础变量 ===== */
:root{
  --bg:#f6f7fb;
  --panel:#ffffff;
  --ink:#161a23;
  --ink-2:#39414f;
  --muted:#767d8d;
  --line:#e6e8f0;
  --line-2:#eff1f7;
  --brand:#4f46e5;
  --brand-2:#7c3aed;
  --brand-soft:#eef0ff;
  --basic:#0369a1;   --basic-bg:#e8f5ff;
  --medium:#a15c07;  --medium-bg:#fdf2e3;
  --hard:#b91c46;    --hard-bg:#ffe9ee;
  --ok:#15803d;
  --radius:16px;
  --mono:"JetBrains Mono","Cascadia Code","Cascadia Mono",Consolas,"Courier New",monospace;
  --sans:"Segoe UI",-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;
}

*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  font-family:var(--sans);
  font-size:15px;
  line-height:1.65;
  color:var(--ink);
  background:
    radial-gradient(900px 380px at 78% -120px, #e9e7ff 0%, rgba(233,231,255,0) 70%),
    radial-gradient(700px 320px at 8% -80px, #e4f3ff 0%, rgba(228,243,255,0) 70%),
    var(--bg);
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;text-decoration:none;}
h1,h2,h3,h4{margin:0;line-height:1.3;letter-spacing:-.01em;}
p{margin:0;}
code{font-family:var(--mono);}

/* ===== 布局 ===== */
.wrap{
  max-width:1280px;
  margin:0 auto;
  padding:26px 24px 80px;
  display:grid;
  grid-template-columns:262px minmax(0,1fr);
  gap:26px;
  align-items:start;
}

/* ===== 侧边栏 ===== */
.side{
  position:sticky;
  top:24px;
  background:var(--panel);
  border:1px solid var(--line);
  border-radius:var(--radius);
  padding:16px 14px;
  box-shadow:0 1px 2px rgba(20,26,40,.04), 0 12px 28px -22px rgba(20,26,40,.25);
  max-height:calc(100vh - 48px);
  overflow:auto;
}
.brand{display:flex;align-items:center;gap:10px;padding:4px 6px 14px;}
.brand-logo{
  width:34px;height:34px;border-radius:10px;flex:none;
  background:linear-gradient(135deg,var(--brand) 0%,var(--brand-2) 100%);
  color:#fff;display:grid;place-items:center;
  font-family:var(--mono);font-weight:700;font-size:14px;letter-spacing:-.5px;
  box-shadow:0 6px 14px -8px rgba(79,70,229,.9);
}
.brand-t strong{display:block;font-size:14.5px;letter-spacing:-.02em;}
.brand-t span{display:block;font-size:11.5px;color:var(--muted);}

.side-label{
  font-size:11px;letter-spacing:.14em;text-transform:uppercase;
  color:var(--muted);padding:14px 8px 7px;font-weight:600;
}
.nav{display:flex;flex-direction:column;gap:2px;}
.nav-item{
  display:flex;align-items:center;gap:10px;
  padding:7px 9px;border-radius:9px;font-size:13.5px;color:var(--ink-2);
  transition:background .15s,color .15s;
}
.nav-item:hover{background:#f3f4fa;}
.nav-item.active{background:var(--brand-soft);color:var(--brand);font-weight:600;}
.nav-no{
  font-family:var(--mono);font-size:11px;color:var(--muted);
  width:20px;height:20px;border-radius:6px;display:grid;place-items:center;
  background:#f2f3f9;flex:none;
}
.nav-item.active .nav-no{background:#dfe2ff;color:var(--brand);}

.toc{display:flex;flex-direction:column;gap:1px;max-height:270px;overflow:auto;}
.toc a{
  display:flex;align-items:center;gap:8px;
  font-size:12.5px;color:var(--muted);padding:5px 9px;border-radius:7px;
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
}
.toc a:hover{background:#f5f6fb;color:var(--ink-2);}
.toc a .dot{width:6px;height:6px;border-radius:50%;flex:none;}
.dot.basic{background:#38bdf8;}
.dot.medium{background:#f59e0b;}
.dot.hard{background:#f43f5e;}

.side-progress{margin-top:16px;padding:12px;border-radius:12px;background:#fafbff;border:1px solid var(--line-2);}
.side-progress .row{display:flex;justify-content:space-between;font-size:12px;color:var(--muted);margin-bottom:7px;}
.side-progress .row b{color:var(--ink);font-family:var(--mono);font-size:12px;}

/* ===== 进度条 ===== */
.bar{height:6px;border-radius:99px;background:#e9ebf4;overflow:hidden;}
.bar > i{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,var(--brand),var(--brand-2));transition:width .4s cubic-bezier(.2,.8,.2,1);}

/* ===== 主区 ===== */
.main{min-width:0;}
.crumb{
  display:inline-flex;align-items:center;gap:8px;
  font-size:12px;color:var(--brand);font-weight:600;letter-spacing:.04em;
  background:var(--brand-soft);padding:4px 11px;border-radius:99px;margin-bottom:14px;
}
h1.page-title{font-size:31px;letter-spacing:-.03em;font-weight:700;}
.page-lede{color:var(--muted);font-size:14px;margin-top:10px;max-width:760px;}
.head-meta{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px;}
.pill{
  font-size:12px;color:var(--ink-2);background:var(--panel);
  border:1px solid var(--line);border-radius:99px;padding:4px 12px;
  display:inline-flex;align-items:center;gap:6px;
}
.pill .led{width:6px;height:6px;border-radius:50%;background:#94a3b8;}
.pill[data-env="ready"] .led{background:#22c55e;box-shadow:0 0 0 3px rgba(34,197,94,.16);}
.pill[data-env="loading"] .led{background:#f59e0b;animation:pulse 1.1s infinite;}
.pill[data-env="error"] .led{background:#ef4444;}
@keyframes pulse{0%,100%{opacity:1}50%{opacity:.25}}

.header-progress{margin-top:18px;display:flex;align-items:center;gap:12px;}
.header-progress .bar{flex:1;height:8px;}
.header-progress span{font-size:12.5px;color:var(--muted);font-family:var(--mono);white-space:nowrap;}

/* ===== 知识点 ===== */
.section-title{
  display:flex;align-items:center;gap:10px;
  margin:30px 0 14px;font-size:15px;font-weight:700;letter-spacing:-.01em;
}
.section-title::before{content:"";width:4px;height:16px;border-radius:99px;background:linear-gradient(180deg,var(--brand),var(--brand-2));}
.section-title span{font-size:12px;color:var(--muted);font-weight:400;}

.points{display:grid;grid-template-columns:repeat(auto-fill,minmax(232px,1fr));gap:12px;}
.point{
  background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:14px 15px;
  transition:border-color .15s, transform .15s, box-shadow .15s;
}
.point:hover{border-color:#d8dbf0;transform:translateY(-1px);box-shadow:0 10px 24px -20px rgba(20,26,40,.5);}
.point h4{font-size:13.5px;margin-bottom:9px;display:flex;align-items:center;gap:6px;}
.point h4::before{content:"";width:5px;height:5px;border-radius:2px;background:var(--brand);transform:rotate(45deg);}
.point pre{
  margin:0;font-family:var(--mono);font-size:12px;line-height:1.65;
  color:#2c3444;background:#f7f8fc;border:1px solid var(--line-2);
  border-radius:9px;padding:9px 10px;overflow-x:auto;white-space:pre;
}
.point p{font-size:12px;color:var(--muted);margin-top:8px;line-height:1.55;}

/* ===== 工具栏 ===== */
.toolbar{
  display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;
  margin:26px 0 14px;
}
.filters{display:flex;gap:6px;background:var(--panel);border:1px solid var(--line);padding:4px;border-radius:12px;}
.filters button{
  border:0;background:transparent;font-family:var(--sans);font-size:13px;color:var(--muted);
  padding:6px 13px;border-radius:9px;cursor:pointer;display:flex;align-items:center;gap:6px;
  transition:background .15s,color .15s;
}
.filters button:hover{background:#f4f5fa;color:var(--ink-2);}
.filters button.on{background:var(--brand);color:#fff;box-shadow:0 6px 14px -10px rgba(79,70,229,.9);}
.filters button .n{font-family:var(--mono);font-size:11px;opacity:.65;}
.tool-note{font-size:12px;color:var(--muted);}
.tool-note b{color:var(--ink-2);font-weight:600;}

/* ===== 练习卡片 ===== */
.ex-list{display:flex;flex-direction:column;gap:16px;}
.ex{
  position:relative;
  background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);
  padding:20px 22px 18px 24px;
  box-shadow:0 1px 2px rgba(20,26,40,.03);
  transition:box-shadow .2s, border-color .2s;
  scroll-margin-top:24px;
}
.ex::before{
  content:"";position:absolute;left:0;top:18px;bottom:18px;width:3px;border-radius:0 4px 4px 0;
  background:#cbd5e1;opacity:.85;
}
.ex[data-level="basic"]::before{background:linear-gradient(180deg,#7dd3fc,#38bdf8);}
.ex[data-level="medium"]::before{background:linear-gradient(180deg,#fcd34d,#f59e0b);}
.ex[data-level="hard"]::before{background:linear-gradient(180deg,#fb7185,#f43f5e);}
.ex:hover{border-color:#dcdfec;box-shadow:0 16px 34px -30px rgba(20,26,40,.6);}
.ex.done{border-color:#d6f0dd;background:linear-gradient(180deg,#fcfffd, #ffffff 60%);}

.ex-head{display:flex;align-items:flex-start;gap:12px;margin-bottom:12px;}
.ex-no{
  font-family:var(--mono);font-size:12px;font-weight:600;color:var(--muted);
  width:30px;height:30px;border-radius:9px;background:#f4f5fa;display:grid;place-items:center;flex:none;
  margin-top:1px;
}
.ex-title-wrap{flex:1;min-width:0;}
.ex-title{font-size:15.5px;font-weight:650;letter-spacing:-.01em;display:flex;align-items:center;gap:9px;flex-wrap:wrap;}
.lv{font-size:11px;font-weight:600;padding:2px 8px;border-radius:99px;letter-spacing:.02em;}
.lv-basic{color:var(--basic);background:var(--basic-bg);}
.lv-medium{color:var(--medium);background:var(--medium-bg);}
.lv-hard{color:var(--hard);background:var(--hard-bg);}
.ex-tags{display:flex;gap:6px;flex-wrap:wrap;margin-top:7px;}
.ex-tags i{
  font-style:normal;font-family:var(--mono);font-size:11px;color:#5b6472;
  background:#f5f6fa;border:1px solid var(--line-2);border-radius:6px;padding:1px 7px;
}

.done-btn{
  border:1px solid var(--line);background:#fff;border-radius:9px;
  font-family:var(--sans);font-size:12px;color:var(--muted);padding:6px 11px;cursor:pointer;
  display:flex;align-items:center;gap:6px;flex:none;transition:all .15s;
}
.done-btn:hover{border-color:#bfe6cb;color:var(--ok);}
.done-btn.on{background:#ecfdf3;border-color:#bfe6cb;color:var(--ok);}
.done-btn .tick{font-size:11px;}

.ex-desc{font-size:13.8px;color:var(--ink-2);line-height:1.72;}
.ex-desc p + p{margin-top:8px;}
.ex-desc ul{margin:8px 0 0;padding-left:20px;color:var(--ink-2);}
.ex-desc li{margin:3px 0;}
.ex-desc b{color:var(--ink);font-weight:650;}
.io{
  margin:10px 0 0;font-family:var(--mono);font-size:12.5px;line-height:1.7;
  background:#f8f9fd;border:1px solid var(--line-2);border-left:3px solid #d9dcf0;
  border-radius:9px;padding:10px 13px;overflow-x:auto;white-space:pre;color:#2c3444;
}
.io .cmt{color:#98a1b3;}
.ex-desc code.k{
  font-size:12.5px;background:#f4f5fa;border:1px solid var(--line-2);
  border-radius:5px;padding:1px 5px;color:#4b3cc4;
}

/* ===== 编辑器 ===== */
.editor{margin-top:14px;border:1px solid var(--line);border-radius:12px;overflow:hidden;background:#fbfcff;}
.ed-bar{
  display:flex;align-items:center;justify-content:space-between;
  padding:7px 12px;background:#f5f6fb;border-bottom:1px solid var(--line-2);
  font-size:11.5px;color:var(--muted);font-family:var(--mono);
}
.ed-bar .dots{display:flex;gap:5px;}
.ed-bar .dots i{width:8px;height:8px;border-radius:50%;background:#dfe2ec;display:block;}
.ed-bar .dots i:nth-child(1){background:#fda4af;}
.ed-bar .dots i:nth-child(2){background:#fcd34d;}
.ed-bar .dots i:nth-child(3){background:#86efac;}
.ed-body{position:relative;}
.ed-body > textarea.code,
.ed-body > .hl{
  box-sizing:border-box;margin:0;width:100%;
  padding:14px 16px;
  font-family:var(--mono);font-size:13.4px;line-height:1.88;
  letter-spacing:normal;tab-size:4;
  white-space:pre-wrap;overflow-wrap:break-word;word-break:normal;
  border:0;text-align:left;
}
.ed-body > .hl{
  position:absolute;inset:0;overflow:hidden;pointer-events:none;
  background:#fbfcff;color:#1f2633;
}
.ed-body > .hl code{display:block;font:inherit;white-space:inherit;}
textarea.code{
  position:relative;z-index:1;display:block;resize:none;outline:0;
  min-height:200px;background:transparent;
  color:transparent;caret-color:#1f2633;
}
textarea.code::selection{background:rgba(79,70,229,.22);}
textarea.code::placeholder{color:#b6bccb;}

/* 语法高亮配色 */
.tk-kw{color:#7c3aed;font-weight:600;}
.tk-st{color:#0f766e;}
.tk-cm{color:#9aa3b5;font-style:italic;}
.tk-nu{color:#b45309;}
.tk-bi{color:#0369a1;}

/* ===== 操作按钮 ===== */
.actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:12px;align-items:center;}
.btn{
  border:1px solid var(--line);background:#fff;color:var(--ink-2);
  font-family:var(--sans);font-size:12.8px;font-weight:500;
  padding:7px 14px;border-radius:9px;cursor:pointer;
  display:inline-flex;align-items:center;gap:6px;transition:all .15s;
}
.btn:hover{background:#f7f8fc;border-color:#d8dbea;}
.btn:active{transform:translateY(1px);}
.btn.primary{
  background:linear-gradient(135deg,var(--brand),var(--brand-2));color:#fff;border-color:transparent;
  box-shadow:0 8px 18px -12px rgba(79,70,229,.95);font-weight:600;
}
.btn.primary:hover{filter:brightness(1.06);}
.btn.primary:disabled{opacity:.6;cursor:progress;}
.btn.ghost{background:transparent;border-color:transparent;color:var(--muted);}
.btn.ghost:hover{background:#f4f5fa;color:var(--ink-2);}
.btn .spin{
  width:11px;height:11px;border:2px solid rgba(255,255,255,.5);border-top-color:#fff;
  border-radius:50%;animation:rot .7s linear infinite;
}
@keyframes rot{to{transform:rotate(360deg)}}

/* ===== 提示 / 输出 / 答案 ===== */
.panel{margin-top:12px;border-radius:12px;padding:12px 14px;font-size:13px;}
.hint-box{background:#fffbeb;border:1px solid #fde9b8;color:#7c5305;}
.hint-box b{font-size:12px;letter-spacing:.04em;display:block;margin-bottom:4px;color:#a16207;}

.out-box{background:#f8fafc;border:1px solid var(--line);border-radius:12px;overflow:hidden;}
.out-bar{
  display:flex;align-items:center;justify-content:space-between;
  padding:6px 12px;background:#f1f3f9;border-bottom:1px solid var(--line-2);
  font-size:11.5px;color:var(--muted);font-family:var(--mono);
}
.out-bar .st{display:flex;align-items:center;gap:6px;}
.out-bar .st i{width:6px;height:6px;border-radius:50%;background:#cbd5e1;display:block;}
.out-box.ok .st i{background:#22c55e;}
.out-box.err .st i{background:#ef4444;}
pre.stdout{
  margin:0;padding:12px 14px;font-family:var(--mono);font-size:12.8px;line-height:1.72;
  white-space:pre-wrap;word-break:break-word;color:#1f2633;max-height:340px;overflow:auto;
}
pre.stdout:empty::before{content:"（没有输出）";color:#aeb5c4;font-style:italic;}
pre.stdout .e{color:#b91c46;}
pre.stdout .m{color:#7c8698;font-style:italic;}
.figs{display:flex;flex-wrap:wrap;gap:10px;padding:0 14px 12px;}
.figs img{max-width:100%;border:1px solid var(--line);border-radius:8px;background:#fff;}

.ans-box{background:#f7f5ff;border:1px solid #e4dcff;border-radius:12px;overflow:hidden;}
.ans-box .ans-title{
  padding:8px 14px;font-size:12px;color:#6d28d9;font-weight:600;
  background:#efeaff;border-bottom:1px solid #e4dcff;
  display:flex;align-items:center;justify-content:space-between;
}
pre.sol{
  margin:0;padding:12px 14px;font-family:var(--mono);font-size:12.8px;line-height:1.75;
  white-space:pre;overflow-x:auto;color:#241f3d;background:#fbfaff;
}
.ans-note{
  padding:10px 14px;font-size:12.5px;color:#4c4467;line-height:1.7;
  border-top:1px dashed #ddd3ff;background:#fbfaff;
}
.ans-note b{color:#5b21b6;}

.hidden{display:none !important;}

/* ===== 页脚 ===== */
.foot{
  margin-top:44px;padding-top:18px;border-top:1px solid var(--line);
  font-size:12px;color:var(--muted);display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;
}

/* ===== 首页 ===== */
.hero{
  grid-column:1 / -1;
  background:var(--panel);border:1px solid var(--line);border-radius:22px;
  padding:38px 40px;position:relative;overflow:hidden;
  box-shadow:0 1px 2px rgba(20,26,40,.04),0 30px 60px -50px rgba(20,26,40,.5);
}
.hero::after{
  content:"";position:absolute;right:-70px;top:-90px;width:320px;height:320px;border-radius:50%;
  background:radial-gradient(circle,rgba(124,58,237,.14),rgba(124,58,237,0) 68%);
}
.hero h1{font-size:38px;letter-spacing:-.035em;margin-top:14px;}
.hero h1 em{
  font-style:normal;background:linear-gradient(120deg,var(--brand),var(--brand-2) 60%,#db2777);
  -webkit-background-clip:text;background-clip:text;color:transparent;
}
.hero p{color:var(--muted);margin-top:12px;max-width:640px;font-size:14.5px;}
.hero-stats{display:flex;gap:26px;margin-top:26px;flex-wrap:wrap;position:relative;z-index:1;}
.hero-stats div{display:flex;flex-direction:column;}
.hero-stats b{font-size:24px;font-family:var(--mono);letter-spacing:-.03em;}
.hero-stats span{font-size:12px;color:var(--muted);}

.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:16px;margin-top:22px;}
.card{
  background:var(--panel);border:1px solid var(--line);border-radius:18px;padding:20px 22px;
  display:flex;flex-direction:column;gap:12px;
  transition:transform .18s, box-shadow .18s, border-color .18s;
  position:relative;overflow:hidden;
}
.card:hover{transform:translateY(-3px);border-color:#d7daf0;box-shadow:0 24px 40px -34px rgba(20,26,40,.75);}
.card-top{display:flex;align-items:center;justify-content:space-between;gap:10px;}
.card-no{font-family:var(--mono);font-size:11.5px;color:var(--brand);background:var(--brand-soft);padding:3px 9px;border-radius:99px;font-weight:600;}
.card-tag{font-size:11px;color:var(--muted);}
.card h3{font-size:17px;letter-spacing:-.02em;}
.card .sub{font-size:12.5px;color:var(--muted);line-height:1.6;flex:1;}
.card-foot{display:flex;align-items:center;gap:10px;margin-top:2px;}
.card-foot .bar{flex:1;}
.card-foot .n{font-size:11.5px;font-family:var(--mono);color:var(--muted);white-space:nowrap;}
.tips{
  grid-column:1 / -1;
  background:#fff;border:1px dashed #d9dcf0;border-radius:18px;padding:22px 26px;
}
.tips h3{font-size:14.5px;margin-bottom:10px;}
.tips ul{margin:0;padding-left:20px;color:var(--ink-2);font-size:13.2px;line-height:1.9;}
.tips code{font-size:12.5px;background:#f4f5fa;border-radius:5px;padding:1px 6px;border:1px solid var(--line-2);}

.wrap.home{grid-template-columns:minmax(0,1fr);gap:0;}

/* ===== 滚动条（避免代码块出现粗重的灰色条） ===== */
pre::-webkit-scrollbar{height:7px;width:7px;}
pre::-webkit-scrollbar-track{background:transparent;}
pre::-webkit-scrollbar-thumb{background:#d9dded;border-radius:99px;}
pre::-webkit-scrollbar-thumb:hover{background:#c3c9e0;}
.point pre::-webkit-scrollbar{height:6px;}
.point pre::-webkit-scrollbar-thumb{background:transparent;}
.point pre:hover::-webkit-scrollbar-thumb{background:#dcdfec;}

/* ===== 响应式 ===== */
@media (max-width:1080px){
  .wrap{grid-template-columns:1fr;padding:18px 16px 60px;}
  .side{position:static;max-height:none;order:-1;}
  .nav{max-height:236px;overflow:auto;}
  .toc{max-height:180px;}
  .hero{padding:28px 22px;}
  .hero h1{font-size:29px;}
}
@media (max-width:640px){
  .ex{padding:16px 16px 14px 18px;}
  h1.page-title{font-size:24px;}
  .hero-stats{gap:18px;}
  .brand{padding-bottom:8px;}
}