:root{
  --green:#58cc02;--green-d:#46a302;--green-l:#d7ffb8;
  --blue:#1cb0f6;--blue-d:#1899d6;--blue-l:#ddf4ff;
  --red:#ff4b4b;--red-d:#ea2b2b;--red-l:#ffdfe0;
  --gold:#ffc800;--gold-d:#e5a500;
  --purple:#ce82ff;--purple-d:#a560cc;
  --gray:#e5e5e5;--gray-d:#afafaf;--text:#3c3c3c;--muted:#777;
  --bg:#fff;--card:#fff;--radius:16px;
}
*{box-sizing:border-box}
html,body{margin:0;background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Apple SD Gothic Neo","Noto Sans KR",Roboto,sans-serif;font-size:16px;line-height:1.5}
button{font:inherit;cursor:pointer}
code,pre{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace}

/* topbar */
.topbar{position:sticky;top:0;z-index:5;display:flex;justify-content:space-between;align-items:center;padding:10px 16px;background:#fff;border-bottom:2px solid var(--gray)}
.brand{font-weight:800;font-size:20px;color:var(--green);letter-spacing:-.5px}
.crab{filter:drop-shadow(0 1px 0 rgba(0,0,0,.15))}
.stats{display:flex;gap:14px;font-weight:700;color:var(--muted)}
.stat b{color:var(--text)}
.stat .ico{margin-right:3px}

.view{max-width:640px;margin:0 auto;padding:16px 16px 90px}

/* tabs */
.tabs{position:fixed;bottom:0;left:0;right:0;display:flex;justify-content:space-around;background:#fff;border-top:2px solid var(--gray);padding:6px 0 max(6px,env(safe-area-inset-bottom));z-index:5}
.tabs button{background:none;border:0;display:flex;flex-direction:column;align-items:center;gap:2px;font-size:22px;color:var(--muted);padding:4px 14px;border-radius:12px}
.tabs button span{font-size:11px;font-weight:700}
.tabs button.active{background:var(--blue-l);color:var(--blue-d);outline:2px solid #84d8ff}

/* buttons */
.btn{display:inline-block;border:0;border-radius:14px;padding:12px 22px;font-weight:800;text-transform:none;letter-spacing:.3px;color:#fff;background:var(--green);box-shadow:0 4px 0 var(--green-d);transition:transform .05s,box-shadow .05s;user-select:none}
.btn:active{transform:translateY(4px);box-shadow:0 0 0 var(--green-d)}
.btn:disabled{background:var(--gray);box-shadow:0 4px 0 #cfcfcf;color:var(--gray-d);cursor:default}
.btn.blue{background:var(--blue);box-shadow:0 4px 0 var(--blue-d)}
.btn.red{background:var(--red);box-shadow:0 4px 0 var(--red-d)}
.btn.ghost{background:#fff;color:var(--blue);box-shadow:0 4px 0 var(--gray);border:2px solid var(--gray)}
.btn.wide{width:100%}

/* path */
.section{margin:26px 0 12px}
.section-hd{background:var(--green);color:#fff;border-radius:var(--radius);padding:14px 18px;box-shadow:0 4px 0 var(--green-d)}
.section-hd small{opacity:.85;font-weight:700;letter-spacing:1px;font-size:12px}
.section-hd h2{margin:2px 0 0;font-size:20px}
.section:nth-of-type(2n) .section-hd{background:var(--blue);box-shadow:0 4px 0 var(--blue-d)}
.section:nth-of-type(3n) .section-hd{background:var(--purple);box-shadow:0 4px 0 var(--purple-d)}
.chapter{margin:20px 0 6px}
.chapter-hd{display:flex;align-items:center;gap:12px;padding:10px 14px;border:2px solid var(--gray);border-radius:var(--radius);background:#fafafa}
.chapter-hd .em{font-size:28px}
.chapter-hd h3{margin:0;font-size:16px}
.chapter-hd small{color:var(--muted);font-weight:600}
.chapter-hd .pct{margin-left:auto;font-weight:800;color:var(--green-d)}
.nodes{display:flex;flex-direction:column;align-items:center;gap:14px;padding:16px 0 4px}
.node{position:relative;width:74px;height:70px;border:0;border-radius:50%;background:var(--gray);box-shadow:0 8px 0 var(--gray-d);font-size:28px;color:#fff;display:flex;align-items:center;justify-content:center;transition:transform .05s}
.node:active{transform:translateY(6px);box-shadow:0 2px 0 var(--gray-d)}
.node.done{background:var(--gold);box-shadow:0 8px 0 var(--gold-d)}
.node.active{background:var(--green);box-shadow:0 8px 0 var(--green-d);animation:pulse 1.6s infinite}
.node.locked{cursor:not-allowed}
.node .lbl{position:absolute;top:-30px;left:50%;transform:translateX(-50%);background:#fff;color:var(--green);border:2px solid var(--gray);border-radius:10px;padding:3px 10px;font-size:12px;font-weight:800;white-space:nowrap;animation:bob 1.2s infinite}
.node .lbl:after{content:"";position:absolute;left:50%;bottom:-7px;width:10px;height:10px;background:#fff;border-right:2px solid var(--gray);border-bottom:2px solid var(--gray);transform:translateX(-50%) rotate(45deg)}
.node .title{position:absolute;top:76px;left:50%;transform:translateX(-50%);color:var(--muted);font-size:12px;font-weight:700;white-space:nowrap;max-width:200px;overflow:hidden;text-overflow:ellipsis}
.node-wrap{height:100px;display:flex;justify-content:center}
.node-wrap.l{transform:translateX(-60px)}.node-wrap.r{transform:translateX(60px)}
@keyframes pulse{0%,100%{transform:scale(1)}50%{transform:scale(1.05)}}
@keyframes bob{0%,100%{transform:translate(-50%,0)}50%{transform:translate(-50%,-4px)}}

/* cards / generic */
.card{border:2px solid var(--gray);border-radius:var(--radius);padding:16px;margin:12px 0;background:var(--card)}
.card h3{margin:0 0 6px}
.muted{color:var(--muted)}
.row{display:flex;gap:10px;align-items:center;flex-wrap:wrap}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.big{font-size:32px;font-weight:900}
.tag{display:inline-block;padding:2px 8px;border-radius:8px;font-size:12px;font-weight:800;background:var(--gray)}
.tag.ok{background:var(--green-l);color:var(--green-d)}
table.cur{width:100%;border-collapse:collapse;font-size:14px}
table.cur td,table.cur th{padding:8px 6px;border-bottom:1px solid var(--gray);text-align:left;vertical-align:top}
table.cur tr.lesson td:first-child{padding-left:26px;color:var(--muted)}
table.cur tr.ch td{font-weight:800}
.ach{display:grid;grid-template-columns:repeat(auto-fill,minmax(140px,1fr));gap:10px}
.ach .a{border:2px solid var(--gray);border-radius:14px;padding:12px;text-align:center;opacity:.45;filter:grayscale(1)}
.ach .a.got{opacity:1;filter:none;border-color:var(--gold)}
.ach .a .em{font-size:32px}
.ach .a b{display:block;font-size:13px}
.ach .a small{color:var(--muted);font-size:11px}
.switch{display:flex;align-items:center;gap:8px;font-weight:700}

/* progress bar */
.bar{height:16px;background:var(--gray);border-radius:8px;overflow:hidden;flex:1}
.bar i{display:block;height:100%;background:var(--green);border-radius:8px;transition:width .3s}
.bar i:after{content:"";display:block;height:5px;margin:3px 8px;background:rgba(255,255,255,.35);border-radius:3px}

/* lesson overlay */
#lesson{position:fixed;inset:0;background:#fff;z-index:20;display:flex;flex-direction:column}
#lesson[hidden]{display:none}
.lesson .hd{display:flex;align-items:center;gap:14px;padding:14px 16px;max-width:760px;width:100%;margin:0 auto}
.lesson .hd .x{border:0;background:none;font-size:24px;color:var(--gray-d);padding:4px}
.hearts{font-weight:800;color:var(--red);white-space:nowrap}
.lesson .body{flex:1;overflow:auto;padding:8px 16px 24px}
.lesson .inner{max-width:640px;margin:0 auto}
.lesson .ft{border-top:2px solid var(--gray);padding:14px 16px max(14px,env(safe-area-inset-bottom))}
.lesson .ft .inner{display:flex;justify-content:space-between;align-items:center;gap:12px}
.lesson .ft.ok{background:var(--green-l);border-color:transparent}
.lesson .ft.bad{background:var(--red-l);border-color:transparent}
.fb{flex:1}
.fb h4{margin:0 0 4px;font-size:20px}
.ft.ok .fb{color:var(--green-d)}.ft.bad .fb{color:var(--red-d)}
.fb p{margin:0;font-size:14px;color:inherit}

/* study */
.study h2{margin:6px 0 4px}
.study .md p{margin:10px 0}
.study .md pre{margin:12px 0}
.kp{background:var(--blue-l);border-radius:var(--radius);padding:12px 16px 12px 32px;margin:16px 0}
.kp li{margin:4px 0;font-weight:600}

/* exercise */
.q{font-size:20px;font-weight:800;margin:10px 0 14px}
pre.code{background:#2b2b2b;color:#f2f2f2;padding:14px;border-radius:12px;overflow:auto;font-size:14px;line-height:1.5;margin:0 0 14px;white-space:pre}
.k{color:#cc7832}.s{color:#6a8759}.c{color:#808080;font-style:italic}.m{color:#ffc66d}.n{color:#6897bb}.t{color:#a9b7c6}
.blank{display:inline-block;min-width:60px;border-bottom:2px dashed var(--blue);color:var(--blue);text-align:center;padding:0 4px;font-weight:800}
.opts{display:flex;flex-direction:column;gap:10px}
.opt{text-align:left;border:2px solid var(--gray);border-bottom-width:4px;border-radius:14px;padding:12px 14px;background:#fff;font-weight:600;color:var(--text);display:flex;gap:10px;align-items:flex-start;transition:background .1s}
.opt .i{min-width:26px;height:26px;border:2px solid var(--gray);border-radius:8px;display:inline-flex;align-items:center;justify-content:center;font-size:12px;color:var(--muted);font-weight:800}
.opt code{font-size:14px;white-space:pre-wrap}
.opt.sel{border-color:#84d8ff;background:var(--blue-l);color:var(--blue-d)}
.opt.sel .i{border-color:#84d8ff;color:var(--blue-d)}
.opt.right{border-color:var(--green);background:var(--green-l);color:var(--green-d)}
.opt.wrong{border-color:var(--red);background:var(--red-l);color:var(--red-d)}
.opt:disabled{cursor:default}
.opts.tf{flex-direction:row}
.opts.tf .opt{flex:1;justify-content:center;font-size:18px}
/* order */
.slots{min-height:60px;border:2px dashed var(--gray);border-radius:14px;padding:10px;display:flex;flex-direction:column;gap:6px;margin-bottom:14px}
.chip{border:2px solid var(--gray);border-bottom-width:4px;border-radius:12px;background:#fff;padding:8px 12px;font-family:ui-monospace,Menlo,monospace;font-size:14px;text-align:left;white-space:pre}
.chips{display:flex;flex-wrap:wrap;gap:8px}
.slots .chip{background:var(--blue-l);border-color:#84d8ff}
/* match */
.mgrid{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.mcol{display:flex;flex-direction:column;gap:10px}
.mcol .opt{min-height:56px;align-items:center}
.opt.paired{border-color:var(--gray);background:#f7f7f7;color:var(--gray-d);pointer-events:none}
.shake{animation:shake .3s}
@keyframes shake{0%,100%{transform:translateX(0)}25%{transform:translateX(-6px)}75%{transform:translateX(6px)}}

/* result */
.result{text-align:center;padding:40px 0}
.result .em{font-size:80px;animation:pop .5s}
.result h2{margin:8px 0 20px}
.result .grid2 .card{margin:0}
.result .card small{display:block;font-weight:800;font-size:12px;letter-spacing:1px}
.result .card.xp{border-color:var(--gold);color:var(--gold-d)}
.result .card.acc{border-color:var(--green);color:var(--green-d)}
@keyframes pop{0%{transform:scale(.3)}70%{transform:scale(1.15)}100%{transform:scale(1)}}

.hero{background:linear-gradient(135deg,var(--green),#7ed957);color:#fff;border-radius:20px;padding:22px;margin-bottom:8px}
.hero h1{margin:0 0 4px;font-size:26px}
.hero p{margin:0;opacity:.95}
.empty{text-align:center;color:var(--muted);padding:40px 10px}
@media (max-width:480px){.node-wrap.l{transform:translateX(-44px)}.node-wrap.r{transform:translateX(44px)}.stats{gap:10px;font-size:14px}}

/* playground */
.runwrap{margin:12px 0}
.runwrap pre.code{margin-bottom:0;border-radius:12px 12px 0 0}
.runbar{display:flex;gap:10px;align-items:center;background:#1f1f1f;padding:8px 12px;border-radius:0 0 12px 12px}
.runbar .run{border:0;border-radius:10px;padding:6px 14px;font-weight:800;color:#fff;background:var(--green);box-shadow:0 3px 0 var(--green-d)}
.runbar .run:disabled{background:var(--gray-d);box-shadow:none}
.runbar .pg{margin-left:auto;color:#9cdcfe;font-size:13px;font-weight:700;text-decoration:none}
.runbar .pg:hover{text-decoration:underline}
pre.out{margin:0;background:#0d1117;color:#7ee787;border:1px solid #333;border-top:0;border-radius:0 0 12px 12px;padding:12px 14px;font-size:13px;white-space:pre-wrap;word-break:break-all;max-height:300px;overflow:auto}
pre.out.err{color:#ffa198}
.runwrap:has(.out:not([hidden])) .runbar{border-radius:0}
.runbar .norun{color:#bbb;font-size:12px;font-weight:700}