@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: normal;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-ext-400-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: normal;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-400-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: normal;
  font-display: swap;
  font-weight: 700;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-ext-700-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: normal;
  font-display: swap;
  font-weight: 700;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-700-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: italic;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-ext-400-italic.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Atkinson Hyperlegible';
  font-style: italic;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/atkinson-hyperlegible-latin-400-italic.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 500;
  src: url(/assets/fonts/bricolage-grotesque-latin-ext-500-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 500;
  src: url(/assets/fonts/bricolage-grotesque-latin-500-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 700;
  src: url(/assets/fonts/bricolage-grotesque-latin-ext-700-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 700;
  src: url(/assets/fonts/bricolage-grotesque-latin-700-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 800;
  src: url(/assets/fonts/bricolage-grotesque-latin-ext-800-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'Bricolage Grotesque';
  font-style: normal;
  font-display: swap;
  font-weight: 800;
  src: url(/assets/fonts/bricolage-grotesque-latin-800-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/jetbrains-mono-latin-ext-400-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/jetbrains-mono-latin-400-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-display: swap;
  font-weight: 600;
  src: url(/assets/fonts/jetbrains-mono-latin-ext-600-normal.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-display: swap;
  font-weight: 600;
  src: url(/assets/fonts/jetbrains-mono-latin-600-normal.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: italic;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/jetbrains-mono-latin-ext-400-italic.woff2) format('woff2');
  unicode-range: U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF;
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: italic;
  font-display: swap;
  font-weight: 400;
  src: url(/assets/fonts/jetbrains-mono-latin-400-italic.woff2) format('woff2');
  unicode-range: U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD;
}

/* Layout: an engineering notebook — sticky tool bar over graph paper; each lesson is a text column beside a workbench (editor + live output). */
:root{
  --paper:#F4F6FB; --surface:#FFFFFF; --surface-2:#EDF1F8; --ink:#152036; --ink-2:#4B5872; --line:#D7DEEA; --line-2:#BFC9DA;
  --accent:#2445D6; --accent-ink:#FFFFFF; --accent-soft:#E2E8FF; --mark:#FFD84A; --mark-ink:#352A00;
  --ok:#0F7F55; --ok-soft:#DCF2E8; --warn:#9A620A; --warn-soft:#FBEED5; --bad:#C3343C; --bad-soft:#FBE3E4;
  --grid:rgba(36,69,214,.055); --term-bg:#152036; --term-fg:#EEF2FA;
  --code-bg:#FBFCFE; --code-gutter:#F0F3F9; --code-fg:#1D2740; --code-dim:#97A2B7; --code-sel:rgba(36,69,214,.20); --code-caret:#2445D6; --code-cur:rgba(255,216,74,.38);
  --t-tg:#B4236C; --t-at:#8A5600; --t-st:#0F7A55; --t-kw:#2445D6; --t-fn:#7A3FC4; --t-nu:#B4521C; --t-cm:#8592A8; --t-vl:#0E6C8A; --t-pn:#6B7891;
  --shadow:0 1px 2px rgba(21,32,54,.06),0 10px 28px rgba(21,32,54,.07);
  --f-display:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif;
  --f-body:"Atkinson Hyperlegible","Segoe UI",system-ui,-apple-system,sans-serif;
  --f-mono:"JetBrains Mono",ui-monospace,"SFMono-Regular",Menlo,Consolas,monospace;
  --fs:16px; --r:10px; --r-lg:16px;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --paper:#0C1220; --surface:#131B2D; --surface-2:#19233A; --ink:#E6EBF5; --ink-2:#A2AEC5; --line:#27324A; --line-2:#3A4763;
  --accent:#8DA4FF; --accent-ink:#0C1220; --accent-soft:#1D2952; --mark:#FFD84A; --mark-ink:#2B2200;
  --ok:#3DD598; --ok-soft:#10342A; --warn:#F0B54A; --warn-soft:#3A2C10; --bad:#FF7B83; --bad-soft:#3D1A1E;
  --grid:rgba(141,164,255,.05); --term-bg:#05080F; --term-fg:#DCE3F2;
  --code-bg:#0E1526; --code-gutter:#0A101D; --code-fg:#DCE3F2; --code-dim:#56627C; --code-sel:rgba(141,164,255,.28); --code-caret:#FFD84A; --code-cur:rgba(255,216,74,.16);
  --t-tg:#FF8DC0; --t-at:#FFC86B; --t-st:#7EE2B0; --t-kw:#8DA4FF; --t-fn:#C9A2FF; --t-nu:#FFA36B; --t-cm:#6C7993; --t-vl:#6FD3F2; --t-pn:#8793AB;
  --shadow:0 1px 2px rgba(0,0,0,.35),0 10px 28px rgba(0,0,0,.28);
  color-scheme:dark;
}}
:root[data-theme="dark"]{
  --paper:#0C1220; --surface:#131B2D; --surface-2:#19233A; --ink:#E6EBF5; --ink-2:#A2AEC5; --line:#27324A; --line-2:#3A4763;
  --accent:#8DA4FF; --accent-ink:#0C1220; --accent-soft:#1D2952; --mark:#FFD84A; --mark-ink:#2B2200;
  --ok:#3DD598; --ok-soft:#10342A; --warn:#F0B54A; --warn-soft:#3A2C10; --bad:#FF7B83; --bad-soft:#3D1A1E;
  --grid:rgba(141,164,255,.05); --term-bg:#05080F; --term-fg:#DCE3F2;
  --code-bg:#0E1526; --code-gutter:#0A101D; --code-fg:#DCE3F2; --code-dim:#56627C; --code-sel:rgba(141,164,255,.28); --code-caret:#FFD84A; --code-cur:rgba(255,216,74,.16);
  --t-tg:#FF8DC0; --t-at:#FFC86B; --t-st:#7EE2B0; --t-kw:#8DA4FF; --t-fn:#C9A2FF; --t-nu:#FFA36B; --t-cm:#6C7993; --t-vl:#6FD3F2; --t-pn:#8793AB;
  --shadow:0 1px 2px rgba(0,0,0,.35),0 10px 28px rgba(0,0,0,.28);
  color-scheme:dark;
}
*{box-sizing:border-box}
html{font-size:var(--fs)}
body{
  margin:0; background-color:var(--paper); color:var(--ink); font-family:var(--f-body); font-size:1rem; line-height:1.6;
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:24px 24px;
}
body::before{content:"";position:fixed;inset:0 0 auto;height:env(safe-area-inset-top,0px);z-index:40;background:var(--surface)}
a{color:var(--accent)}
:focus-visible{outline:3px solid var(--accent);outline-offset:2px;border-radius:6px}
h1,h2,h3,h4{font-family:var(--f-display);line-height:1.15;text-wrap:balance;margin:0;letter-spacing:-.01em}
p{margin:0}
code,kbd,pre{font-family:var(--f-mono)}
code{font-size:.88em;background:var(--surface-2);border:1px solid var(--line);border-radius:5px;padding:.05em .35em}
pre code{background:none;border:0;padding:0;font-size:inherit;border-radius:0;color:inherit}
mark{background:var(--mark);color:var(--mark-ink);padding:0 .2em;border-radius:3px}
.wrap{max-width:1240px;margin:0 auto;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.muted{color:var(--ink-2)}
.eyebrow{font-size:.78rem;letter-spacing:.09em;text-transform:uppercase;font-weight:700;color:var(--ink-2)}

/* ---------- top bar ---------- */
.top{position:sticky;top:env(safe-area-inset-top,0px);z-index:30;background:var(--surface);border-bottom:1px solid var(--line)}
.top-in{display:flex;align-items:center;gap:16px;min-height:60px;flex-wrap:wrap;padding-block:6px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink);font-family:var(--f-display);font-weight:800;font-size:1.2rem;letter-spacing:-.02em}
.brand svg{width:32px;height:32px;flex:none}
.nav{display:flex;gap:2px;flex:1;min-width:0;overflow-x:auto;scrollbar-width:none}
.nav::-webkit-scrollbar{display:none}
.nav a{white-space:nowrap;text-decoration:none;color:var(--ink-2);font-weight:700;padding:8px 12px;border-radius:8px;font-size:.95rem}
.nav a:hover{color:var(--ink);background:var(--surface-2)}
.nav a[aria-current="page"]{color:var(--accent);background:var(--accent-soft)}
.tools{display:flex;align-items:center;gap:8px;margin-left:auto}
.search-btn{display:flex;align-items:center;gap:8px;border:1px solid var(--line);background:var(--paper);color:var(--ink-2);border-radius:999px;padding:6px 12px;font:inherit;font-size:.9rem;cursor:pointer}
.search-btn svg{width:16px;height:16px}
.search-btn kbd{font-size:.72rem;border:1px solid var(--line);border-radius:5px;padding:0 5px;background:var(--surface)}
.pill{display:inline-flex;align-items:center;gap:5px;padding:5px 10px;border-radius:999px;font-weight:700;font-size:.88rem;text-decoration:none;font-variant-numeric:tabular-nums;white-space:nowrap}
.pill svg{width:15px;height:15px}
.pill.xp{background:var(--mark);color:var(--mark-ink)}
.pill.streak{background:var(--surface-2);color:var(--ink);border:1px solid var(--line)}
.pill.streak svg{color:var(--warn)}
.pill.bump{animation:bump .5s ease}
@keyframes bump{30%{transform:scale(1.18)}}
.acct{display:flex;align-items:center;gap:8px;text-decoration:none;color:var(--ink);border-radius:999px}
.acct img,.acct .ava{width:32px;height:32px;border-radius:50%;border:2px solid var(--line);background:var(--surface-2);display:grid;place-items:center;object-fit:cover}
.acct .ava svg{width:18px;height:18px;color:var(--ink-2)}
@media (max-width:480px){.brand span{display:none}}
@media (max-width:820px){
  .nav{order:3;flex-basis:100%;margin:0 -4px}
  .search-btn span,.search-btn kbd{display:none}
}

/* ---------- buttons, chips ---------- */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;font:inherit;font-weight:700;font-size:.95rem;border-radius:9px;padding:9px 16px;border:1px solid var(--line-2);background:var(--surface);color:var(--ink);cursor:pointer;text-decoration:none;line-height:1.2}
.btn:hover{border-color:var(--accent);color:var(--accent)}
.btn svg{width:17px;height:17px;flex:none}
.btn.primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn.primary:hover{filter:brightness(1.08);color:var(--accent-ink)}
.btn.ghost{background:transparent;border-color:transparent;color:var(--ink-2)}
.btn.ghost:hover{background:var(--surface-2);color:var(--ink)}
.btn.small{padding:6px 11px;font-size:.86rem;border-radius:8px}
.btn.warn{border-color:var(--bad);color:var(--bad)}
.btn[disabled]{opacity:.5;cursor:not-allowed}
.chip{display:inline-flex;align-items:center;gap:5px;font-size:.8rem;font-weight:700;padding:3px 9px;border-radius:999px;background:var(--surface-2);color:var(--ink-2);border:1px solid var(--line);white-space:nowrap}
.chip.ok{background:var(--ok-soft);color:var(--ok);border-color:transparent}
.chip.accent{background:var(--accent-soft);color:var(--accent);border-color:transparent}
.chip.mark{background:var(--mark);color:var(--mark-ink);border-color:transparent}
.chip svg{width:13px;height:13px}
.bar{height:8px;border-radius:99px;background:var(--surface-2);overflow:hidden;border:1px solid var(--line)}
.bar > i{display:block;height:100%;background:var(--accent);border-radius:99px;transition:width .4s ease}
.bar.mark > i{background:var(--mark)}

/* ---------- page sections ---------- */
main{padding-block:28px 64px;min-height:70vh}
.page-head{display:flex;align-items:flex-end;justify-content:space-between;gap:16px;flex-wrap:wrap;margin-bottom:24px}
.page-head h1{font-size:clamp(1.9rem,3.6vw,2.6rem);font-weight:800}
.page-head p{max-width:62ch;color:var(--ink-2);margin-top:6px}
.section{margin-top:44px}
.section > h2{font-size:1.45rem;font-weight:800;margin-bottom:6px}
.section > p.lede{color:var(--ink-2);max-width:62ch;margin-bottom:18px}
.panel-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);box-shadow:var(--shadow)}

/* ---------- home ---------- */
.hero{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.05fr);gap:40px;align-items:center;padding-block:20px 8px}
.hero h1{font-size:clamp(2.3rem,5.2vw,4rem);font-weight:800;letter-spacing:-.035em;line-height:1.02}
.hero h1 .hl{background:linear-gradient(transparent 58%,var(--mark) 58%,var(--mark) 92%,transparent 92%);padding:0 .08em}
.hero p.sub{font-size:1.15rem;color:var(--ink-2);max-width:46ch;margin-top:18px}
.hero .cta{display:flex;gap:10px;flex-wrap:wrap;margin-top:26px}
.facts{display:flex;gap:18px;flex-wrap:wrap;margin-top:26px;color:var(--ink-2);font-size:.92rem}
.facts b{color:var(--ink);font-variant-numeric:tabular-nums}
.demo{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);box-shadow:var(--shadow);overflow:hidden}
.demo-head{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:10px 14px;border-bottom:1px solid var(--line);flex-wrap:wrap}
.demo-task{display:flex;align-items:center;gap:8px;font-size:.92rem;font-weight:700}
.demo-body{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr)}
.demo-body .ed{border:0;border-radius:0;height:210px;border-right:1px solid var(--line)}
.demo-body iframe{width:100%;height:210px;border:0;background:#fff;display:block}
.tick{width:20px;height:20px;border-radius:50%;border:2px solid var(--line-2);display:grid;place-items:center;flex:none;transition:all .25s}
.tick svg{width:12px;height:12px;opacity:0;color:var(--accent-ink)}
.done > .tick,.tick.on{background:var(--ok);border-color:var(--ok)}
.done > .tick svg,.tick.on svg{opacity:1;color:#fff}
.paths{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:14px}
.path{position:relative;display:flex;flex-direction:column;gap:10px;padding:18px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);text-decoration:none;color:var(--ink);transition:border-color .2s, transform .2s}
.path:hover{border-color:var(--accent);transform:translateY(-2px)}
.path .tag{font-family:var(--f-mono);font-weight:600;font-size:.82rem;color:var(--accent)}
.path h3{font-size:1.25rem;font-weight:800}
.path p{color:var(--ink-2);font-size:.93rem;flex:1}
.path .row{display:flex;justify-content:space-between;align-items:center;font-size:.85rem;color:var(--ink-2);font-variant-numeric:tabular-nums}
.how{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:0;counter-reset:how;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);overflow:hidden}
.how li{list-style:none;padding:20px;border-right:1px solid var(--line);counter-increment:how}
.how li:last-child{border-right:0}
.how li::before{content:"Step " counter(how);display:block;font-family:var(--f-mono);font-size:.78rem;color:var(--accent);font-weight:600;margin-bottom:8px}
.how h3{font-size:1.08rem;margin-bottom:6px}
.how p{color:var(--ink-2);font-size:.93rem}
.feat{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:28px 32px}
.feat div{border-top:2px solid var(--ink);padding-top:12px}
.feat h3{font-size:1.08rem;margin-bottom:6px}
.feat p{color:var(--ink-2);font-size:.95rem}
@media (max-width:900px){
  .hero{grid-template-columns:1fr}
  .how{grid-template-columns:1fr 1fr}
  .how li:nth-child(2){border-right:0}
  .how li:nth-child(-n+2){border-bottom:1px solid var(--line)}
  .feat{grid-template-columns:1fr 1fr}
}
@media (max-width:560px){
  .demo-body{grid-template-columns:1fr}
  .demo-body .ed{border-right:0;border-bottom:1px solid var(--line)}
  .how{grid-template-columns:1fr}
  .how li{border-right:0;border-bottom:1px solid var(--line)}
  .feat{grid-template-columns:1fr}
}

/* ---------- learn ---------- */
.track{display:grid;grid-template-columns:240px minmax(0,1fr);gap:24px;padding:22px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);margin-bottom:16px}
.track-side h2{font-size:1.5rem;font-weight:800}
.track-side .tag{font-family:var(--f-mono);font-size:.85rem;color:var(--accent);font-weight:600}
.track-side p{color:var(--ink-2);font-size:.93rem;margin:8px 0 14px}
.track-side .bar{margin:8px 0 6px}
.lesson-list{list-style:none;margin:0;padding:0;display:grid;gap:4px}
.lesson-list a,.lesson-list .soon{display:flex;align-items:center;gap:12px;padding:10px 12px;border-radius:10px;text-decoration:none;color:var(--ink)}
.lesson-list a:hover{background:var(--surface-2)}
.lesson-list .num{font-family:var(--f-mono);font-size:.8rem;color:var(--ink-2);width:22px;flex:none}
.lesson-list .t{flex:1;min-width:0;font-weight:700}
.lesson-list .m{font-size:.84rem;color:var(--ink-2);white-space:nowrap}
.lesson-list .soon{color:var(--ink-2)}
.lesson-list .soon .t{font-weight:400}
.lesson-list .soon svg{width:15px;height:15px}
@media (max-width:760px){.track{grid-template-columns:1fr}}

/* ---------- lesson workbench ---------- */
.lesson{display:grid;grid-template-columns:minmax(0,.92fr) minmax(0,1.08fr);gap:24px;align-items:start}
.lesson-text{display:flex;flex-direction:column;gap:18px;min-width:0}
.crumbs{font-size:.88rem;color:var(--ink-2);display:flex;gap:6px;flex-wrap:wrap}
.crumbs a{color:var(--ink-2)}
.lesson-text h1{font-size:clamp(1.8rem,3vw,2.35rem);font-weight:800}
.meta{display:flex;gap:8px;flex-wrap:wrap}
.prose{display:flex;flex-direction:column;gap:12px;font-size:1.04rem;max-width:62ch}
.prose ul{margin:0;padding-left:1.2em}
.term{border-bottom:2px dotted var(--accent);cursor:help;position:relative;font-weight:700}
.term:hover::after,.term:focus::after{content:attr(data-def);position:absolute;left:0;top:calc(100% + 6px);width:min(280px,70vw);background:var(--ink);color:var(--paper);font-weight:400;font-size:.88rem;line-height:1.45;padding:9px 11px;border-radius:9px;z-index:5;box-shadow:var(--shadow)}
.tip{display:flex;gap:10px;padding:12px 14px;background:var(--accent-soft);border-radius:var(--r);font-size:.95rem}
.tip svg{width:20px;height:20px;flex:none;color:var(--accent);margin-top:2px}
.tasks{border:1px solid var(--line);background:var(--surface);border-radius:var(--r-lg);padding:16px 18px}
.tasks-head{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-bottom:10px;flex-wrap:wrap}
.tasks h2{font-size:1.15rem;font-weight:800}
.task-list{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.task-list li{display:flex;gap:10px;align-items:flex-start}
.task-list .tick{margin-top:3px}
.task-list .tt{flex:1;min-width:0}
.task-list .why{display:block;font-size:.86rem;color:var(--bad);font-family:var(--f-mono);margin-top:2px;overflow-wrap:anywhere}
.task-list li.done .tt{color:var(--ink-2)}
.success{margin-top:14px;padding:14px;border-radius:12px;background:var(--ok-soft);display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}
.success b{color:var(--ok)}
.success.claimed{background:var(--surface-2)}
.help-row{display:flex;gap:8px;flex-wrap:wrap}
.hints{display:grid;gap:8px}
.hints .hint{padding:10px 12px;border-left:3px solid var(--mark);background:var(--surface);border-radius:0 8px 8px 0;font-size:.95rem}
.qc{border:1px dashed var(--line-2);border-radius:var(--r-lg);padding:16px}
.qc h3{font-size:1rem;margin-bottom:8px}
.qc .opts{display:grid;gap:6px;margin-top:10px}
.opt{text-align:left;font:inherit;padding:10px 12px;border-radius:9px;border:1px solid var(--line);background:var(--surface);color:var(--ink);cursor:pointer;display:flex;gap:10px;align-items:center}
.opt:hover{border-color:var(--accent)}
.opt.right{border-color:var(--ok);background:var(--ok-soft)}
.opt.wrong{border-color:var(--bad);background:var(--bad-soft)}
.opt code{background:transparent;border:0;padding:0}
.explain{margin-top:10px;font-size:.95rem;padding:10px 12px;border-radius:8px;background:var(--surface-2)}
.pager{display:flex;justify-content:space-between;gap:10px;flex-wrap:wrap;padding-top:8px;border-top:1px solid var(--line)}
.bench{position:sticky;top:calc(env(safe-area-inset-top,0px) + 76px);display:flex;flex-direction:column;gap:10px;min-width:0}
.bench-bar{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap}
.file{font-family:var(--f-mono);font-size:.85rem;color:var(--ink-2);display:flex;align-items:center;gap:8px}
.file b{color:var(--ink);font-weight:600}
.bench-actions{display:flex;gap:6px;flex-wrap:wrap}
.out{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);overflow:hidden}
.tabs{display:flex;gap:2px;border-bottom:1px solid var(--line);padding:4px 6px 0;background:var(--surface-2);overflow-x:auto}
.tabs button{font:inherit;font-size:.88rem;font-weight:700;color:var(--ink-2);background:transparent;border:0;padding:8px 12px;border-radius:8px 8px 0 0;cursor:pointer;display:flex;gap:6px;align-items:center;white-space:nowrap}
.tabs button[aria-selected="true"]{background:var(--surface);color:var(--ink);box-shadow:0 -2px 0 var(--accent) inset}
.count{font-size:.72rem;background:var(--line);color:var(--ink);border-radius:99px;padding:0 6px;min-width:18px;text-align:center}
.count.bad{background:var(--bad);color:#fff}
.count.warn{background:var(--warn);color:#fff}
.tab-panel{height:260px;overflow:auto}
.tab-panel iframe{width:100%;height:100%;border:0;background:#fff;display:block}
.console{font-family:var(--f-mono);font-size:.85rem;margin:0;padding:8px 0}
.console .ln{padding:4px 14px;border-bottom:1px solid var(--line);white-space:pre-wrap;overflow-wrap:anywhere}
.console .ln.error{color:var(--bad);background:var(--bad-soft)}
.console .ln.warn{color:var(--warn);background:var(--warn-soft)}
.empty{padding:18px;color:var(--ink-2);font-size:.92rem}
.problem{display:flex;gap:10px;padding:10px 14px;border-bottom:1px solid var(--line);font-size:.93rem;cursor:pointer;background:transparent;border-left:0;border-right:0;border-top:0;width:100%;text-align:left;font-family:inherit;color:var(--ink)}
.problem:hover{background:var(--surface-2)}
.problem .ln-no{font-family:var(--f-mono);font-size:.8rem;color:var(--ink-2);white-space:nowrap;padding-top:2px}
.problem .sev{width:8px;height:8px;border-radius:50%;flex:none;margin-top:8px;background:var(--warn)}
.problem.error .sev{background:var(--bad)}
.problem small{display:block;color:var(--ink-2);font-family:var(--f-mono);font-size:.8rem;overflow-wrap:anywhere}
@media (max-width:980px){
  .lesson{display:flex;flex-direction:column;gap:18px;align-items:stretch}
  .lesson-text{display:contents}
  .bench{position:static;order:1}
  .lesson-text > .tasks,.lesson-text > .help-row,.lesson-text > .hints,.lesson-text > .tutor,.lesson-text > .qc,.lesson-text > .pager{order:2}
}

/* ---------- editor ---------- */
.ed{display:grid;grid-template-columns:auto minmax(0,1fr);background:var(--code-bg);border:1px solid var(--line);border-radius:var(--r);overflow:hidden;font-family:var(--f-mono);font-size:14px;line-height:1.6;height:var(--ed-h,330px);position:relative}
.ed-gut{background:var(--code-gutter);color:var(--code-dim);overflow:hidden;user-select:none;border-right:1px solid var(--line)}
.ed-gut pre{margin:0;padding:12px 10px 40px 12px;text-align:right;font:inherit;line-height:inherit;min-width:2.6em}
.ed-main{position:relative;overflow:hidden;min-width:0}
.ed-main pre,.ed-main textarea{margin:0;padding:12px 14px 40px;font:inherit;line-height:inherit;white-space:pre;tab-size:2;border:0;letter-spacing:0;word-spacing:0;width:100%;height:100%;box-sizing:border-box}
.ed-main pre{position:absolute;inset:0;overflow:hidden;color:var(--code-fg);pointer-events:none}
.ed-main textarea{position:relative;display:block;resize:none;background:transparent;color:transparent;-webkit-text-fill-color:transparent;caret-color:var(--code-caret);outline:none;overflow:auto}
.ed-main textarea::selection{background:var(--code-sel);-webkit-text-fill-color:transparent}
.ed:focus-within{border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.ed .flash{position:absolute;left:0;right:0;height:1.6em;background:var(--code-cur);pointer-events:none;transition:opacity .8s}
.t-tg{color:var(--t-tg)}.t-at{color:var(--t-at)}.t-st{color:var(--t-st)}.t-kw{color:var(--t-kw);font-weight:600}.t-fn{color:var(--t-fn)}.t-nu{color:var(--t-nu)}.t-cm{color:var(--t-cm);font-style:italic}.t-vl{color:var(--t-vl)}.t-pn{color:var(--t-pn)}
@media (max-width:600px){.ed{font-size:16px}}

/* ---------- tutor ---------- */
.tutor{border:1px solid var(--accent);border-radius:var(--r-lg);background:var(--surface);overflow:hidden}
.tutor-head{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:10px 14px;background:var(--accent-soft)}
.tutor-head h3{font-size:1rem;display:flex;gap:8px;align-items:center}
.tutor-head svg{width:18px;height:18px;color:var(--accent)}
.tutor-body{padding:12px 14px;display:grid;gap:10px}
.tutor-quick{display:flex;gap:6px;flex-wrap:wrap}
.tutor-ask{display:flex;gap:6px}
.tutor-ask input{flex:1;min-width:0;font:inherit;padding:8px 10px;border-radius:8px;border:1px solid var(--line-2);background:var(--paper);color:var(--ink)}
.tutor-out{font-size:.97rem;display:grid;gap:8px}
.tutor-out:empty{display:none}
.tutor-out pre{background:var(--code-bg);border:1px solid var(--line);border-radius:8px;padding:10px;overflow-x:auto;margin:0;font-size:.85rem}
.tutor-note{font-size:.8rem;color:var(--ink-2)}
body:not(.has-tutor) .needs-tutor{display:none!important}

/* ---------- practice ---------- */
.grid-cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px}
.card-link{display:flex;flex-direction:column;gap:8px;padding:18px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);text-decoration:none;color:var(--ink)}
.card-link:hover{border-color:var(--accent)}
.card-link h3{font-size:1.12rem}
.card-link p{color:var(--ink-2);font-size:.93rem;flex:1}
.card-link .row{display:flex;gap:6px;flex-wrap:wrap;align-items:center}
.daily{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:18px;align-items:center;padding:22px;border-radius:var(--r-lg);background:var(--ink);color:var(--paper)}
.daily h2{font-size:1.5rem}
.daily p{opacity:.85;margin-top:6px}
.daily .btn.primary{background:var(--mark);border-color:var(--mark);color:var(--mark-ink)}
@media (max-width:620px){.daily{grid-template-columns:1fr}}
.quiz{max-width:720px}
.quiz .q{font-size:1.25rem;font-weight:700;font-family:var(--f-display);margin:14px 0 10px}
.quiz pre.snip{background:var(--code-bg);border:1px solid var(--line);border-radius:10px;padding:12px 14px;overflow-x:auto;font-size:.9rem;margin:0 0 12px}
.quiz .opts{display:grid;gap:8px}
.quiz-foot{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-top:16px;flex-wrap:wrap}
.score{font-family:var(--f-display);font-size:3rem;font-weight:800;font-variant-numeric:tabular-nums}
.ex-list{display:grid;gap:6px;margin-top:8px}
.ex-list div{font-family:var(--f-mono);font-size:.85rem;background:var(--surface-2);border-radius:8px;padding:6px 10px;overflow-wrap:anywhere}

/* ---------- playground ---------- */
.pg{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:16px}
.pg .ed{--ed-h:440px;border-radius:0 0 var(--r) var(--r)}
.pg-tabs{display:flex;gap:2px;background:var(--surface-2);border:1px solid var(--line);border-bottom:0;border-radius:var(--r) var(--r) 0 0;padding:4px 6px 0}
.pg-tabs button{font:inherit;font-weight:700;font-size:.88rem;border:0;background:transparent;color:var(--ink-2);padding:8px 12px;border-radius:8px 8px 0 0;cursor:pointer}
.pg-tabs button[aria-selected="true"]{background:var(--code-bg);color:var(--ink)}
.pg-out{display:flex;flex-direction:column;gap:10px;min-width:0}
.pg-frame{height:300px;border:1px solid var(--line);border-radius:var(--r);overflow:hidden;background:#fff}
.pg-frame iframe{width:100%;height:100%;border:0;display:block}
.pg-console{height:130px;overflow:auto;border:1px solid var(--line);border-radius:var(--r);background:var(--surface)}
.toolbar{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin-bottom:12px}
.toolbar select,.field select,.field input{font:inherit;padding:7px 10px;border-radius:8px;border:1px solid var(--line-2);background:var(--surface);color:var(--ink)}
.switch{display:inline-flex;align-items:center;gap:8px;font-size:.9rem;font-weight:700;color:var(--ink-2);cursor:pointer}
.snips{display:flex;gap:6px;flex-wrap:wrap;margin-top:10px}
@media (max-width:900px){.pg{grid-template-columns:1fr}.pg .ed{--ed-h:320px}}

/* ---------- tracer ---------- */
.tracer{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);border:1px solid var(--line);border-radius:var(--r);overflow:hidden;background:var(--surface)}
.tr-code{background:var(--code-bg);font-family:var(--f-mono);font-size:14px;line-height:1.7;overflow:auto;border-right:1px solid var(--line);padding:10px 0}
.tr-code div{white-space:pre;padding:0 14px 0 0;display:flex}
.tr-code div .n{width:2.6em;text-align:right;color:var(--code-dim);padding-right:12px;flex:none;user-select:none}
.tr-code div.cur{background:var(--code-cur);box-shadow:3px 0 0 var(--mark) inset}
.tr-side{padding:14px;display:flex;flex-direction:column;gap:10px;min-width:0}
.tr-note{font-size:.95rem;min-height:3.2em}
.tr-side h4{font-size:.8rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-2);font-family:var(--f-body)}
.tr-vars{width:100%;border-collapse:collapse;font-family:var(--f-mono);font-size:.88rem}
.tr-vars td{padding:5px 8px;border-bottom:1px solid var(--line)}
.tr-vars td:first-child{color:var(--ink-2);width:40%}
.tr-vars tr.chg td{background:var(--code-cur)}
.tr-out{margin:0;background:var(--term-bg);color:var(--term-fg);border-radius:8px;padding:10px;font-size:.88rem;min-height:3em;white-space:pre-wrap}
.tr-controls{grid-column:1/-1;display:flex;gap:8px;align-items:center;justify-content:space-between;padding:10px 14px;border-top:1px solid var(--line);flex-wrap:wrap;background:var(--surface-2)}
.tr-controls span{font-variant-numeric:tabular-nums;font-size:.9rem;color:var(--ink-2)}
@media (max-width:700px){.tracer{grid-template-columns:1fr}.tr-code{border-right:0;border-bottom:1px solid var(--line)}}

/* ---------- profile ---------- */
.prof-head{display:flex;gap:18px;align-items:center;flex-wrap:wrap}
.prof-head img{width:72px;height:72px;border-radius:50%;border:3px solid var(--mark);object-fit:cover;background:var(--surface-2)}
.prof-head .ava-big{width:72px;height:72px;border-radius:50%;border:3px solid var(--mark);display:grid;place-items:center;background:var(--surface-2)}
.prof-head .ava-big svg{width:34px;height:34px;color:var(--ink-2)}
.prof-head h1{font-size:2rem;font-weight:800}
.stats{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px;margin-top:22px}
.stat{padding:16px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg)}
.stat .k{font-size:.8rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-2);font-weight:700}
.stat .v{font-family:var(--f-display);font-size:2rem;font-weight:800;font-variant-numeric:tabular-nums;line-height:1.1;margin-top:4px}
.stat .s{font-size:.86rem;color:var(--ink-2);margin-top:6px}
.ring{width:84px;height:84px}
.days{display:grid;grid-template-columns:repeat(14,1fr);gap:4px;max-width:420px}
.days i{aspect-ratio:1;border-radius:4px;background:var(--surface-2);border:1px solid var(--line);max-width:100%}
.days i.on{background:var(--ok);border-color:var(--ok)}
.days i.today{outline:2px solid var(--accent);outline-offset:1px}
.badges{display:grid;grid-template-columns:repeat(auto-fill,minmax(170px,1fr));gap:12px}
.badge{display:flex;gap:12px;align-items:center;padding:12px;border-radius:12px;border:1px solid var(--line);background:var(--surface)}
.badge .medal{width:44px;height:44px;border-radius:50%;display:grid;place-items:center;flex:none;background:var(--surface-2);color:var(--ink-2)}
.badge .medal svg{width:22px;height:22px}
.badge.got .medal{background:var(--mark);color:var(--mark-ink)}
.badge:not(.got){opacity:.62}
.badge b{display:block;font-size:.95rem}
.badge small{color:var(--ink-2);font-size:.82rem;line-height:1.35;display:block}
.cert{position:relative;padding:22px 24px;border:2px solid var(--ink);border-radius:6px;background:var(--surface);box-shadow:6px 6px 0 var(--mark);max-width:520px}
.cert .eyebrow{color:var(--accent)}
.cert h3{font-size:1.5rem;margin:6px 0 4px}
.cert .who{font-family:var(--f-display);font-size:1.2rem}
.cert .id{font-family:var(--f-mono);font-size:.78rem;color:var(--ink-2);margin-top:12px}
.settings{display:grid;gap:14px;max-width:560px}
.field{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;padding:12px 0;border-bottom:1px solid var(--line)}
.field label{font-weight:700}
.field input[type=range]{accent-color:var(--accent);padding:0}
.seg{display:inline-flex;border:1px solid var(--line-2);border-radius:9px;overflow:hidden}
.seg button{font:inherit;font-size:.88rem;font-weight:700;border:0;background:var(--surface);color:var(--ink-2);padding:7px 12px;cursor:pointer}
.seg button[aria-pressed="true"]{background:var(--accent);color:var(--accent-ink)}
@media (max-width:760px){.stats{grid-template-columns:1fr 1fr}}

/* ---------- pro ---------- */
.plans{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px;align-items:stretch}
.plan{display:flex;flex-direction:column;gap:12px;padding:20px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg)}
.plan.best{border:2px solid var(--accent);box-shadow:var(--shadow)}
.plan h3{font-size:1.25rem}
.price{font-family:var(--f-display);font-weight:800;font-size:2.2rem;line-height:1;font-variant-numeric:tabular-nums}
.price small{font-family:var(--f-body);font-size:.9rem;font-weight:400;color:var(--ink-2)}
.plan ul{list-style:none;padding:0;margin:0;display:grid;gap:7px;flex:1;font-size:.93rem}
.plan li{display:flex;gap:8px}
.plan li svg{width:16px;height:16px;color:var(--ok);flex:none;margin-top:4px}
.services{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px}
.svc{padding:18px;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);display:flex;flex-direction:column;gap:8px}
.svc .p{font-weight:700;font-variant-numeric:tabular-nums}
.note{font-size:.88rem;color:var(--ink-2);padding:10px 14px;border:1px dashed var(--line-2);border-radius:10px}
.cmp{width:100%;border-collapse:collapse;font-size:.93rem;min-width:620px}
.cmp th,.cmp td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top}
.cmp th{font-size:.8rem;text-transform:uppercase;letter-spacing:.07em;color:var(--ink-2)}
.cmp td:first-child{font-weight:700}
.scroll-x{overflow-x:auto;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface)}
@media (max-width:1000px){.plans{grid-template-columns:1fr 1fr}}
@media (max-width:560px){.plans{grid-template-columns:1fr}}

/* ---------- modal, toasts, footer ---------- */
.modal{position:fixed;inset:0;z-index:60;background:rgba(10,15,28,.55);display:flex;align-items:flex-start;justify-content:center;padding:calc(env(safe-area-inset-top,0px) + 8vh) max(16px,env(safe-area-inset-right,0px)) 16px max(16px,env(safe-area-inset-left,0px))}
.modal-box{width:min(640px,100%);background:var(--surface);border-radius:var(--r-lg);box-shadow:var(--shadow);border:1px solid var(--line);overflow:hidden;max-height:80vh;display:flex;flex-direction:column}
.modal-box input{font:inherit;font-size:1.1rem;padding:16px 18px;border:0;border-bottom:1px solid var(--line);background:var(--surface);color:var(--ink);outline:none;width:100%}
.results{overflow:auto;padding:6px}
.res{display:flex;gap:12px;align-items:center;width:100%;text-align:left;font:inherit;color:var(--ink);background:transparent;border:0;padding:10px 12px;border-radius:9px;cursor:pointer}
.res:hover,.res.sel{background:var(--accent-soft)}
.res .k{font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.07em;color:var(--ink-2);width:76px;flex:none}
.res .t{flex:1;min-width:0}
.res small{display:block;color:var(--ink-2);font-size:.85rem;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.ref{padding:20px;display:grid;gap:12px;overflow:auto}
.ref pre{background:var(--code-bg);border:1px solid var(--line);border-radius:10px;padding:12px;overflow-x:auto;margin:0;font-size:.88rem}
.toasts{position:fixed;right:max(16px,env(safe-area-inset-right,0px));bottom:calc(16px + env(safe-area-inset-bottom,0px));z-index:70;display:grid;gap:8px;justify-items:end}
.toast{background:var(--ink);color:var(--paper);padding:10px 14px;border-radius:10px;box-shadow:var(--shadow);font-weight:700;display:flex;gap:10px;align-items:center;animation:up .3s ease;max-width:min(380px,calc(100vw - 32px))}
.toast .x{background:var(--mark);color:var(--mark-ink);padding:1px 8px;border-radius:99px;font-variant-numeric:tabular-nums;white-space:nowrap}
@keyframes up{from{transform:translateY(10px);opacity:0}}
footer{border-top:1px solid var(--line);background:var(--surface);padding-block:36px 24px;font-size:.92rem;color:var(--ink-2)}
.foot{display:grid;grid-template-columns:minmax(0,1.5fr) repeat(4,minmax(0,1fr));gap:24px}
.foot h3{font-family:var(--f-body);font-size:.76rem;text-transform:uppercase;letter-spacing:.09em;color:var(--ink-2);margin-bottom:10px}
.foot ul{list-style:none;padding:0;margin:0;display:grid;gap:7px}
.foot a{color:var(--ink);text-decoration:none}
.foot a:hover{color:var(--accent);text-decoration:underline}
.foot-brand p{margin-top:10px;max-width:34ch}
.foot .brand span{display:inline}
.foot-bottom{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;margin-top:28px;padding-top:16px;border-top:1px solid var(--line);font-size:.85rem}
@media (max-width:820px){.foot{grid-template-columns:1fr 1fr}.foot-brand{grid-column:1/-1}}
.skip{position:absolute;left:-999px;top:8px;z-index:80;background:var(--accent);color:var(--accent-ink);padding:8px 12px;border-radius:8px;border:0;font:inherit;font-weight:700}
.skip:focus{left:16px}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}

/* ---------- polish: header, home, lesson, reference, docs ---------- */
main:focus{outline:none}
.icon-btn{display:inline-grid;place-items:center;width:36px;height:36px;flex:none;border-radius:999px;border:1px solid var(--line);background:var(--paper);color:var(--ink-2);cursor:pointer;text-decoration:none}
.icon-btn:hover{color:var(--ink);border-color:var(--line-2)}
.icon-btn svg{width:18px;height:18px}
.icon-btn.off{opacity:.35;cursor:default}
.hero-search{display:flex;align-items:center;gap:10px;width:100%;max-width:470px;margin-top:22px;padding:12px 16px;border-radius:12px;border:1px solid var(--line-2);background:var(--surface);color:var(--ink-2);font:inherit;font-size:1rem;cursor:text;text-align:left;box-shadow:var(--shadow)}
.hero-search:hover{border-color:var(--accent)}
.hero-search svg{width:18px;height:18px;flex:none}
.hero-search span{flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.hero-search kbd{font-size:.75rem;border:1px solid var(--line);border-radius:5px;padding:0 6px;background:var(--paper)}
.big-num{font-family:var(--f-display);font-weight:800;font-size:1.9rem;line-height:1;color:var(--accent)}
.big-num svg{width:28px;height:28px}
.cta-band{display:flex;justify-content:space-between;align-items:center;gap:18px;flex-wrap:wrap;padding:28px;border-radius:var(--r-lg);background:var(--accent);color:var(--accent-ink)}
.cta-band h2{font-size:1.6rem;font-weight:800}
.cta-band p{opacity:.9;margin-top:6px}
.cta-band .btn{background:var(--mark);border-color:var(--mark);color:var(--mark-ink)}
.cta-band .btn:hover{color:var(--mark-ink);filter:brightness(1.05)}
.track-side h2 a{color:inherit;text-decoration:none}
.track-side h2 a:hover{color:var(--accent)}
h1.big{font-size:clamp(2rem,4vw,2.9rem);font-weight:800;letter-spacing:-.02em;margin-top:8px}
.lede-lg{font-size:1.12rem;color:var(--ink-2);max-width:62ch;margin-top:12px}
.track-hero{display:grid;grid-template-columns:minmax(0,1.35fr) minmax(0,1fr);gap:28px;align-items:start;margin-top:14px}
.track-hero .tag{font-family:var(--f-mono);font-weight:600;font-size:.88rem;color:var(--accent)}
.track-hero .cta{display:flex;gap:10px;flex-wrap:wrap;margin-top:22px}
.side-card{padding:20px;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);display:grid;gap:12px;box-shadow:var(--shadow)}
.side-card h2{font-size:1.15rem}
.outcomes{list-style:none;padding:0;margin:0;display:grid;gap:9px}
.outcomes li{display:flex;gap:10px;font-size:.96rem}
.outcomes svg{width:16px;height:16px;color:var(--ok);flex:none;margin-top:4px}
.lesson-list.boxed{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);padding:8px}
@media (max-width:820px){.track-hero{grid-template-columns:1fr}}
.lesson-top{display:flex;align-items:center;justify-content:space-between;gap:10px;flex-wrap:wrap}
.lesson-nav{display:flex;gap:6px;align-items:center}
.outline{position:relative}
.outline > summary{list-style:none}
.outline > summary::-webkit-details-marker{display:none}
.outline[open] > summary{border-color:var(--accent);color:var(--accent)}
.outline-panel{position:absolute;right:0;top:calc(100% + 6px);z-index:25;width:min(340px,86vw);background:var(--surface);border:1px solid var(--line);border-radius:12px;box-shadow:var(--shadow);padding:6px;max-height:60vh;overflow:auto}
.outline-panel a{display:flex;gap:10px;align-items:center;padding:8px 10px;border-radius:8px;text-decoration:none;color:var(--ink);font-size:.93rem}
.outline-panel a:hover{background:var(--surface-2)}
.outline-panel a[aria-current="page"]{background:var(--accent-soft);color:var(--accent);font-weight:700}
.outline-panel .num{font-family:var(--f-mono);font-size:.78rem;color:var(--ink-2);width:20px;flex:none}
.outline-panel .t{flex:1;min-width:0}
.outline-panel .tick{width:16px;height:16px}
.outline-panel .tick svg{width:10px;height:10px}
.mini-progress{height:4px;border-radius:99px;background:var(--surface-2);overflow:hidden;margin-top:-6px}
.mini-progress i{display:block;height:100%;background:var(--accent);border-radius:99px}
.pager-end{display:flex;gap:8px;flex-wrap:wrap;margin-left:auto}
.example{border:1px solid var(--line);border-radius:var(--r-lg);overflow:hidden;background:var(--surface)}
.example-head{display:flex;justify-content:space-between;align-items:center;gap:8px;padding:8px 12px;border-bottom:1px solid var(--line);background:var(--surface-2)}
.example-head b{font-family:var(--f-display);font-size:.98rem}
.example-head b .muted{font-family:var(--f-body);font-weight:400;font-size:.88rem}
.example pre.code{margin:0;padding:12px 14px;overflow-x:auto;background:var(--code-bg);font-size:.87rem;line-height:1.6;border-left:3px solid var(--accent);color:var(--code-fg)}
.example .out-label{font-size:.74rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-2);font-weight:700;padding:10px 14px 0}
.example .tr-out{margin:8px 14px 14px}
.modal-box.wide{width:min(1100px,100%);max-height:88vh}
.tryit-head{display:flex;justify-content:space-between;align-items:center;gap:10px;padding:12px 16px;border-bottom:1px solid var(--line);flex-wrap:wrap}
.tryit-head h2{font-size:1.1rem}
.tryit-actions{display:flex;gap:6px;flex-wrap:wrap}
.tryit-body{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px;padding:12px 12px 0;overflow:auto}
.tryit-body .ed{--ed-h:360px}
.tryit-out{border:1px solid var(--line);border-radius:var(--r);overflow:hidden;background:#fff;display:flex;min-width:0}
.tryit-out iframe{flex:1;border:0;width:100%;height:360px;display:block}
.tryit-out .console{flex:1;background:var(--surface);height:360px;overflow:auto;margin:0}
.tryit-note{font-size:.85rem;color:var(--ink-2);padding:8px 16px 14px}
@media (max-width:820px){.tryit-body{grid-template-columns:1fr}.tryit-body .ed{--ed-h:220px}.tryit-out iframe,.tryit-out .console{height:220px}}
.ref-tools{display:flex;gap:12px;flex-wrap:wrap;align-items:center;margin-bottom:8px}
.ref-tools input{flex:1 1 260px;min-width:0;font:inherit;padding:10px 12px;border-radius:10px;border:1px solid var(--line-2);background:var(--surface);color:var(--ink)}
.chips-row{display:flex;gap:6px;flex-wrap:wrap}
.lang-chip{display:inline-flex;align-items:center;padding:6px 12px;border-radius:999px;border:1px solid var(--line);background:var(--surface);text-decoration:none;color:var(--ink);font-weight:700;font-size:.88rem}
.lang-chip:hover{border-color:var(--accent);color:var(--accent)}
.lang-chip[aria-current="page"]{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.ref-section h2{font-size:1.35rem;margin:30px 0 12px}
.ref-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(290px,1fr));gap:14px}
.ref-card{display:flex;flex-direction:column;gap:8px;padding:16px;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);min-width:0}
.ref-card h3{font-family:var(--f-mono);font-size:.98rem;font-weight:600;color:var(--accent)}
.ref-card p{font-size:.94rem;color:var(--ink-2)}
.ref-card pre{margin:0;background:var(--code-bg);border:1px solid var(--line);border-radius:8px;padding:10px;overflow-x:auto;font-size:.82rem;color:var(--code-fg)}
.ref-card .row{display:flex;gap:6px;flex-wrap:wrap;margin-top:auto;padding-top:4px}
.ref-card .btn svg{width:14px;height:14px}
.doc{max-width:720px;display:grid;gap:14px;font-size:1.04rem}
.doc h2{font-size:1.35rem;margin-top:14px}
.doc ul{margin:0;padding-left:1.2em;display:grid;gap:6px}
.doc .cta{display:flex;gap:10px;flex-wrap:wrap;margin-top:10px}
.row-gap{display:flex;gap:8px;flex-wrap:wrap}
.btn.soon{opacity:.6;cursor:not-allowed}
.soon-card{opacity:.85}
.quiz pre.snip{color:var(--code-fg)}
.hero > *{min-width:0}
@media (max-width:560px){.hero-search kbd{display:none}}
[hidden]{display:none!important}
img{max-width:100%}