:root{--teal:#2C7A7B;--teal-d:#0f766e;--teal-50:#f0fdfa;--ink:#0f172a;--mute:#64748b;--line:#e8edf3;--bg:#f6f8fb;--card:#fff;--r:16px;--sh:0 1px 2px rgba(15,23,42,.04),0 8px 24px rgba(15,23,42,.06);--side:264px;--ease:cubic-bezier(.2,.7,.2,1)}
*{box-sizing:border-box}html{scroll-behavior:smooth}
body{margin:0;font-family:'Libre Franklin',Inter,-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;color:var(--ink);line-height:1.6;background:var(--bg);-webkit-font-smoothing:antialiased}
a{color:var(--teal-d)}
.top{display:flex;align-items:center;gap:12px;height:60px;padding:0 18px;position:sticky;top:0;z-index:30;background:rgba(255,255,255,.85);backdrop-filter:saturate(1.4) blur(10px);border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:9px;font-weight:800;text-decoration:none;color:var(--ink);letter-spacing:-.01em}.brand b{color:var(--teal)}
.top nav{margin-left:auto;display:flex;align-items:center;gap:18px;font-weight:650;font-size:14px}.top nav a{text-decoration:none;color:#334155}
.top .cta{background:var(--teal);color:#fff!important;padding:8px 14px;border-radius:999px;box-shadow:0 4px 14px rgba(44,122,123,.25);transition:transform .15s var(--ease)}.top .cta:hover{transform:translateY(-1px)}
.burger{display:none;font-size:20px;cursor:pointer;padding:6px 8px;border-radius:10px}.lnav{position:absolute;opacity:0;pointer-events:none}
/* layout */
.lwrap{display:grid;grid-template-columns:var(--side) minmax(0,1fr);transition:grid-template-columns .25s var(--ease)}
body.rail{--side:68px}
.lside{position:sticky;top:60px;height:calc(100vh - 60px);overflow:auto;padding:14px 10px;background:var(--card);border-right:1px solid var(--line)}
.lside .lhead{display:flex;align-items:center;justify-content:space-between;margin:0 4px 10px}
.lside .lt{margin:0;font-weight:800;font-size:12px;text-transform:uppercase;letter-spacing:.06em}.lside .lt a{color:var(--mute);text-decoration:none}
.railbtn{border:1px solid var(--line);background:#fff;border-radius:10px;width:32px;height:32px;cursor:pointer;color:var(--mute);display:flex;align-items:center;justify-content:center;transition:transform .25s var(--ease),background .15s}.railbtn:hover{background:var(--bg)}
body.rail .railbtn{transform:rotate(180deg)}body.rail .lside .lt,body.rail .lside .lbl,body.rail .lside em{display:none}body.rail .lside .lhead{justify-content:center}
.lside ol{list-style:none;padding:0;margin:0}
.lside li a,.lside li>span{display:flex;align-items:center;gap:11px;padding:9px 10px;border-radius:12px;text-decoration:none;color:#334155;font-size:14.5px;font-weight:600;transition:background .15s}
body.rail .lside li a,body.rail .lside li>span{justify-content:center;padding:9px 0}
.lside li a:hover{background:var(--bg)}.lside li.cur a{background:var(--teal-50);color:var(--teal-d);font-weight:800;box-shadow:inset 3px 0 0 var(--teal)}
.lside .ck{width:26px;height:26px;border-radius:50%;background:#eef2f6;display:flex;align-items:center;justify-content:center;font-size:12px;font-weight:800;flex:none;transition:background .2s}
.lside li.done .ck{background:var(--teal);color:#fff;font-size:0}.lside li.done .ck::after{content:'✓';font-size:13px}.lside li.started .ck{background:#ccfbf1;color:var(--teal-d)}
.lside li.soon{opacity:.5}.lside em{font-style:normal;font-size:10.5px;font-weight:700;border:1px solid var(--line);border-radius:99px;padding:0 7px;margin-left:auto;color:var(--mute)}
.scrim{display:none}
main{padding:28px 32px 64px}main>*:not(.exsec){max-width:1000px}
.crumbs{font-size:13px;color:var(--mute)}.crumbs a{color:var(--mute);text-decoration:none}
h1{font-size:36px;line-height:1.15;letter-spacing:-.02em;margin:6px 0 10px}h2{font-size:21px;letter-spacing:-.01em;margin:34px 0 12px;display:flex;align-items:center;gap:10px}
h2 .pill{font-size:12px;background:var(--teal);color:#fff;border-radius:99px;padding:2px 9px;letter-spacing:0}
.lead{font-size:18px;color:#334155;max-width:720px;margin:0 0 6px}.goals{color:#334155}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--r);box-shadow:var(--sh)}
/* home */
.pwrap{padding:16px 18px;max-width:560px;margin:14px 0 6px}.pbar{height:10px;border-radius:99px;background:#eef2f6;overflow:hidden}.pbar span{display:block;height:100%;width:var(--p,0%);background:linear-gradient(90deg,#2dd4bf,var(--teal));transition:width .6s var(--ease)}
.ptext{font-size:13.5px;color:var(--mute);margin:8px 0 0}
.chapters{list-style:none;padding:0;margin:0;display:grid;gap:12px;max-width:780px}
.chapters li{background:var(--card);border:1px solid var(--line);border-radius:var(--r);box-shadow:var(--sh);display:flex;align-items:center;gap:16px;padding:16px 18px;transition:transform .15s var(--ease),box-shadow .15s}
.chapters li:not(.soon):hover{transform:translateY(-2px);box-shadow:0 12px 30px rgba(15,23,42,.09)}
.chapters .num{width:38px;height:38px;border-radius:50%;background:#eef2f6;display:flex;align-items:center;justify-content:center;font-weight:800;flex:none}
.chapters li.done .num{background:var(--teal);color:#fff;font-size:0}.chapters li.done .num::after{content:'✓';font-size:18px}.chapters li.started .num{background:#ccfbf1}
.chapters a{font-weight:800;text-decoration:none;color:var(--ink);font-size:17px}.chapters a::after{content:'';position:absolute;inset:0}.chapters li{position:relative}
.chapters small{display:block;color:var(--mute);font-size:14px}.chapters li.soon{opacity:.55;box-shadow:none}.chapters .tag{margin-left:auto;font-size:11.5px;font-weight:700;color:var(--mute);border:1px solid var(--line);border-radius:99px;padding:2px 9px}
/* demo */
.walk{margin:0;overflow:hidden;max-width:1000px}.walk video{display:block;width:100%;height:auto;background:#fff}.walk p{margin:0;padding:10px 16px;font-size:13.5px;color:var(--mute);border-top:1px solid var(--line)}
/* exercise: full width + height */
.exsec{margin:0 -20px;padding:0}#try{scroll-margin-top:70px}
.ex{display:grid;grid-template-columns:330px minmax(0,1fr);gap:14px}
.panel{padding:18px;align-self:start;position:sticky;top:74px}
.tasks{list-style:none;padding:0;margin:0 0 12px}.tasks li{display:flex;gap:10px;align-items:center;padding:7px 10px;border-radius:10px;font-size:15px;color:var(--mute);transition:background .15s}
.tasks li::before{content:'';width:18px;height:18px;border-radius:50%;border:2px solid #cbd5e1;flex:none;transition:all .2s}.tasks li.cur{background:var(--teal-50);color:var(--ink);font-weight:700}.tasks li.ok{color:var(--ink)}
.tasks li.ok::before{background:var(--teal);border-color:var(--teal);content:'✓';color:#fff;font-size:11px;display:flex;align-items:center;justify-content:center}
.cur-title{font-size:17px;margin:6px 0 4px}.cur-text{font-size:15.5px}.cur-text ol{padding-left:20px;margin:6px 0}
.btns{display:flex;flex-wrap:wrap;gap:8px;margin:14px 0 8px}
.btn{font:inherit;font-weight:750;border-radius:12px;padding:10px 16px;border:1px solid var(--line);background:#fff;cursor:pointer;min-height:44px;transition:transform .12s var(--ease),box-shadow .12s,background .12s}.btn:hover:not(:disabled){transform:translateY(-1px)}
.btn.pri{background:var(--teal);border-color:var(--teal);color:#fff;box-shadow:0 6px 16px rgba(44,122,123,.25)}.btn:disabled{opacity:.45;cursor:not-allowed;transform:none}.btn.link{border:0;background:none;color:var(--mute);font-weight:600;padding:8px 2px;min-height:auto}
.status{border-radius:12px;padding:10px 12px;font-size:15px;margin:8px 0;animation:pop .25s var(--ease)}.status.ok{background:#f0fdf4;border:1px solid #bbf7d0;color:#166534}.status.bad{background:#fff7ed;border:1px solid #fed7aa;color:#9a3412}.status.info{background:#eff6ff;border:1px solid #bfdbfe;color:#1e40af}
.hint{background:#fefce8;border:1px solid #fde68a;border-radius:12px;padding:6px 12px;font-size:15px}.hint p{margin:6px 0}
.next{background:var(--teal-50);border:1px solid #99f6e4;border-radius:12px;padding:12px 14px;margin-top:10px;animation:pop .3s var(--ease)}.next a{font-weight:800}
@keyframes pop{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}
.ed-wrap{position:relative;overflow:hidden;height:calc(100vh - 140px);min-height:560px;display:flex;align-items:center;justify-content:center;background:radial-gradient(circle at 50% 40%,#fff,#f1f5f9)}
.ed-wrap .ed{position:absolute;inset:0;width:100%;height:100%;border:0;background:#fff}
.ed-ph{text-align:center;padding:24px}.ed-ph .ico{width:64px;height:64px;border-radius:18px;background:var(--teal-50);display:flex;align-items:center;justify-content:center;margin:0 auto 10px}.ed-ph p{color:var(--mute);max-width:360px;margin:6px auto 14px}
.txt{max-width:780px}
kbd{border:1px solid #cbd5e1;border-bottom-width:3px;border-radius:6px;padding:0 6px;font:600 13px ui-monospace,monospace;background:#fff}
.foot{padding:22px;text-align:center;font-size:13px;color:var(--mute)}
@media (max-width:1100px){.ex{grid-template-columns:290px minmax(0,1fr)}}
@media (max-width:900px){
 .burger{display:block}.lwrap{display:block}.railbtn{display:none}body.rail{--side:264px}
 body.rail .lside .lt,body.rail .lside .lbl,body.rail .lside em{display:revert}
 .lside{position:fixed;top:0;left:0;bottom:0;width:82vw;max-width:310px;height:100vh;z-index:50;transform:translateX(-102%);transition:transform .25s var(--ease);box-shadow:0 0 40px rgba(0,0,0,.18)}
 .lnav:checked~.lwrap .lside{transform:none}.lnav:checked~.lwrap .scrim{display:block;position:fixed;inset:0;background:rgba(15,23,42,.35);z-index:45}
 main{padding:20px 16px 50px}.exsec{margin:0 -16px;padding:0 8px}.ex{grid-template-columns:1fr}.panel{position:static}
 .ed-wrap{height:78vh;min-height:480px}h1{font-size:28px}.top nav a:not(.cta){display:none}}
@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}
.soonbox{padding:16px 18px;margin:16px 0;max-width:720px}.soonbox .btn{display:inline-flex;align-items:center;text-decoration:none;color:var(--ink)}.soonbox .btn.pri{color:#fff}
/* tabs */
.ctabs{display:flex;gap:8px;margin:22px 0 16px;border-bottom:1px solid var(--line);position:sticky;top:60px;z-index:20;background:var(--bg);padding-top:6px;max-width:none!important}
.ctabs a{display:flex;align-items:center;gap:8px;padding:11px 18px;font-weight:800;font-size:16px;color:var(--mute);text-decoration:none;border-bottom:3px solid transparent;margin-bottom:-1px;border-radius:10px 10px 0 0}
.ctabs a[aria-selected=true]{color:var(--teal-d);border-color:var(--teal);background:#fff}
.ctabs .pill{font-size:12px;background:#cbd5e1;color:#fff;border-radius:99px;padding:2px 9px}.ctabs a[aria-selected=true] .pill{background:var(--teal)}
.vh{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}.after{margin:16px 0}
.panel .ph{margin:0 0 6px;font-size:12px;font-weight:800;text-transform:uppercase;letter-spacing:.06em;color:var(--mute)}
.tasks li::before,.tasks li.ok::before{display:none}.tasks .tn{width:22px;height:22px;border-radius:50%;border:2px solid #cbd5e1;display:flex;align-items:center;justify-content:center;font-size:11px;font-weight:800;flex:none;transition:all .2s}
.tasks li.ok .tn{background:var(--teal);border-color:var(--teal);color:#fff;font-size:0}.tasks li.ok .tn::after{content:'✓';font-size:12px}
.btn.ghost{background:none;color:var(--mute);font-weight:650}
.tick{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;pointer-events:none;opacity:0;z-index:3}
.tick svg{background:rgba(255,255,255,.92);border-radius:50%;box-shadow:0 10px 40px rgba(15,118,110,.25)}.tick circle{fill:none;stroke:var(--teal);stroke-width:3;stroke-dasharray:151;stroke-dashoffset:151}.tick path{fill:none;stroke:var(--teal);stroke-width:4;stroke-linecap:round;stroke-linejoin:round;stroke-dasharray:40;stroke-dashoffset:40}
.ed-wrap.ticked .tick{animation:tk 1.4s var(--ease)}.ed-wrap.ticked .tick circle{animation:dr .5s var(--ease) forwards}.ed-wrap.ticked .tick path{animation:dr .35s .3s var(--ease) forwards}
@keyframes tk{0%{opacity:0;transform:scale(.8)}15%{opacity:1;transform:scale(1)}75%{opacity:1}100%{opacity:0}}@keyframes dr{to{stroke-dashoffset:0}}
.donebox{display:flex;align-items:center;gap:16px;padding:16px 18px;margin:0 0 14px;border-color:#99f6e4;background:var(--teal-50);animation:pop .3s var(--ease);flex-wrap:wrap}.donebox[hidden]{display:none}
.big-ck{width:46px;height:46px;border-radius:50%;background:var(--teal);color:#fff;font-size:24px;display:flex;align-items:center;justify-content:center;flex:none}
.donebox p{margin:0}.dt{font-weight:800;font-size:18px}.dn,.cd{color:var(--mute);font-size:14px}.dbtns{margin-left:auto;display:flex;gap:8px}.dbtns .btn{text-decoration:none;display:inline-flex;align-items:center}
.pnav{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:34px}.pn{display:block;padding:14px 16px;border:1px solid var(--line);border-radius:14px;background:#fff;text-decoration:none;font-weight:750;color:var(--ink)}.pn small{display:block;color:var(--mute);font-weight:600}.pn.next{text-align:right}
@media (max-width:900px){.ctabs{top:60px}.ctabs a{padding:10px 12px;font-size:15px}.dbtns{margin-left:0}}

.qres mark{background:#ccfbf1;color:inherit;border-radius:3px;padding:0 1px}.qres .hh{font-weight:650;color:#334155}
.search{position:relative;flex:1;max-width:420px;margin-left:18px}.search input{width:100%;height:38px;border:1px solid #cbd5e1;border-radius:10px;padding:0 12px;font:inherit;font-size:15px;background:var(--bg)}
.qres{position:absolute;top:44px;left:0;right:0;background:#fff;border:1px solid var(--line);border-radius:12px;box-shadow:0 12px 30px rgba(15,23,42,.12);max-height:70vh;overflow:auto;z-index:60}
.qres a{display:block;padding:10px 12px;text-decoration:none;color:var(--ink);border-bottom:1px solid #f1f5f9;font-weight:650;font-size:14.5px}.qres a:hover,.qres a.on{background:#f0fdfa}.qres small{display:block;color:var(--mute);font-size:12.5px;font-weight:400}.qres .sec{display:block;font-size:11px;font-weight:800;color:var(--teal-d);text-transform:uppercase}
@media (max-width:900px){.top{flex-wrap:wrap;height:auto;padding:8px 12px;row-gap:8px}.search{order:5;flex:1 0 100%;margin:0;max-width:none}.lside{top:0}}
/* levels */
.lvl{display:inline-flex;align-items:center;font-size:11.5px;font-weight:800;letter-spacing:.02em;border-radius:99px;padding:2px 9px;background:#dcfce7;color:#166534}
.lvl-intermediate{background:#fef3c7;color:#92400e}.lvl-advanced{background:#fee2e2;color:#991b1b}
.cmeta{display:flex;gap:10px;align-items:center;color:var(--mute);font-size:13.5px;margin:0 0 8px}.chapters .meta{display:flex;gap:8px;align-items:center;margin-top:6px;font-size:12.5px;color:var(--mute)}
.chips{display:flex;flex-wrap:wrap;gap:6px;margin:0 4px 10px}.chip{font:inherit;font-size:12px;font-weight:700;border:1px solid var(--line);background:#fff;color:#334155;border-radius:99px;padding:4px 10px;cursor:pointer}
.chip[aria-pressed=true]{background:var(--teal);border-color:var(--teal);color:#fff}.home-chips{margin:0 0 12px}
.lvl-empty{font-size:13px;color:var(--mute);margin:4px 6px 10px;background:var(--bg);border-radius:10px;padding:8px 10px}
[data-level].lvl-hide{display:none!important}body.rail .chips,body.rail .lvl-empty{display:none}