:root{
  --bg:#f6f7f9; --panel:#fff; --ink:#1b1f27; --sub:#5b6472; --line:#e3e6eb; --soft:#eef1f5;
  --brand:#1f3a68; --brand-2:#2f6fd6; --accent:#d9480f; --ok:#2b8a3e; --warn:#e8a300; --bad:#c92a2a;
  --check:#fff8e6; --check-line:#f0c36d; --key:#e7f0ff; --red:#c92a2a;
  --radius:10px; --shadow:0 1px 2px rgba(0,0,0,.05),0 2px 8px rgba(0,0,0,.04);
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#12151b; --panel:#1a1e26; --ink:#e7eaf0; --sub:#9aa3b2; --line:#2c323d; --soft:#232833;
  --brand:#8fb3ff; --brand-2:#6ea2ff; --accent:#ff8a50; --check:#2a2412; --check-line:#7a6122; --key:#1d2a44; --red:#ff6b6b;
}}
:root[data-theme="dark"]{
  --bg:#12151b; --panel:#1a1e26; --ink:#e7eaf0; --sub:#9aa3b2; --line:#2c323d; --soft:#232833;
  --brand:#8fb3ff; --brand-2:#6ea2ff; --accent:#ff8a50; --check:#2a2412; --check-line:#7a6122; --key:#1d2a44; --red:#ff6b6b;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:15px/1.7 "Pretendard","Noto Sans KR","Malgun Gothic",system-ui,sans-serif;word-break:keep-all;overflow-wrap:anywhere}
a{color:var(--brand-2);text-decoration:none}
button,input,select,textarea{font:inherit;color:inherit}
h1,h2,h3{line-height:1.35;margin:0 0 .5em}
.wrap{max-width:1080px;margin:0 auto;padding:0 16px}

/* header */
header{background:var(--panel);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}
.top{display:flex;align-items:center;gap:12px;padding:10px 0 6px;flex-wrap:wrap}
.logo{font-weight:800;font-size:17px;color:var(--ink)}
.logo small{display:block;font-weight:500;font-size:12px;color:var(--sub)}
.top .sp{flex:1}
.search{display:flex;gap:6px}
.search input{width:220px;max-width:46vw;border:1px solid var(--line);background:var(--bg);border-radius:8px;padding:6px 10px}
.iconbtn{border:1px solid var(--line);background:var(--panel);border-radius:8px;padding:6px 10px;cursor:pointer}
nav.tabs{display:flex;gap:4px;overflow-x:auto;padding:4px 0 8px;scrollbar-width:none}
nav.tabs::-webkit-scrollbar{display:none}
nav.tabs a{white-space:nowrap;padding:6px 12px;border-radius:8px;color:var(--sub);font-weight:600;font-size:14px}
nav.tabs a:hover{background:var(--soft)}
nav.tabs a.on{background:var(--brand);color:#fff}
:root[data-theme="dark"] nav.tabs a.on{color:#0d1220}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) nav.tabs a.on{color:#0d1220}}

main{padding:20px 0 60px}
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px 20px;box-shadow:var(--shadow);margin-bottom:16px}
.eyebrow{font-size:12px;font-weight:700;color:var(--accent);letter-spacing:.02em}
.muted{color:var(--sub)}
.small{font-size:13px}
.grid{display:grid;gap:12px}
.g2{grid-template-columns:repeat(auto-fit,minmax(260px,1fr))}
.g3{grid-template-columns:repeat(auto-fit,minmax(220px,1fr))}
.g4{grid-template-columns:repeat(auto-fit,minmax(160px,1fr))}
.tile{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:14px 16px}
.tile h3{font-size:15px;margin-bottom:4px}
.tile .num{font-size:24px;font-weight:800;color:var(--brand)}
.btn{display:inline-block;border:1px solid var(--brand);background:var(--brand);color:#fff;border-radius:8px;padding:7px 14px;cursor:pointer;font-weight:600}
:root[data-theme="dark"] .btn{color:#0d1220}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) .btn{color:#0d1220}}
.btn.ghost{background:transparent;color:var(--brand)}
.btn.sm{padding:4px 10px;font-size:13px}
.btn:disabled{opacity:.45;cursor:default}
.row{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.chip{display:inline-block;font-size:12px;padding:1px 8px;border-radius:99px;background:var(--soft);color:var(--sub);font-weight:600}
.chip.p25{background:#fde8e8;color:#a61e1e}
.chip.p10{background:#e6f0ff;color:#1f4f9c}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) .chip.p25{background:#3a1c1c;color:#ff9b9b}:root:not([data-theme="light"]) .chip.p10{background:#1b2a46;color:#9cc0ff}}
:root[data-theme="dark"] .chip.p25{background:#3a1c1c;color:#ff9b9b}
:root[data-theme="dark"] .chip.p10{background:#1b2a46;color:#9cc0ff}
table{border-collapse:collapse;width:100%;font-size:14px}
th,td{border:1px solid var(--line);padding:6px 9px;text-align:left;vertical-align:top}
th{background:var(--soft);font-weight:700}
.tbl{overflow-x:auto;margin:8px 0}
select,input[type=text],input[type=search]{border:1px solid var(--line);background:var(--panel);border-radius:8px;padding:6px 10px}
.filters{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:12px}
.seg{display:inline-flex;border:1px solid var(--line);border-radius:8px;overflow:hidden}
.seg button{border:0;background:var(--panel);padding:5px 12px;cursor:pointer;color:var(--sub);font-weight:600}
.seg button.on{background:var(--brand);color:#fff}

/* question list */
.qlist{list-style:none;margin:0;padding:0}
.qlist li{display:flex;gap:10px;align-items:center;padding:10px 4px;border-bottom:1px solid var(--line)}
.qlist li:last-child{border-bottom:0}
.qlist .id{font-family:ui-monospace,Consolas,monospace;font-size:13px;color:var(--sub);min-width:62px}
.qlist .t{flex:1}
.dot{width:10px;height:10px;border-radius:50%;background:var(--line);flex:none}
.dot.r1{background:var(--bad)}.dot.r2{background:var(--warn)}.dot.r3{background:var(--ok)}

/* answer rendering */
.qbox{border:2px solid var(--brand);border-radius:var(--radius);padding:14px 16px;background:var(--panel);margin-bottom:14px}
.qbox .lab{font-weight:800;color:var(--brand);margin-right:6px}
.src{font-size:13px;color:var(--sub);margin-top:6px}
.subtabs{display:flex;gap:6px;margin:4px 0 14px;border-bottom:1px solid var(--line)}
.subtabs button{border:0;background:none;padding:8px 12px;cursor:pointer;font-weight:700;color:var(--sub);border-bottom:3px solid transparent}
.subtabs button.on{color:var(--brand);border-color:var(--brand)}
.guide{background:var(--soft);border-radius:8px;padding:10px 14px;margin-bottom:12px}
.chunk{border:1px solid var(--line);border-radius:var(--radius);padding:12px 16px;margin-bottom:12px;background:var(--panel)}
.chunk h4{margin:0 0 8px;font-size:15px}
.chunk h4 .n{display:inline-block;background:var(--brand);color:#fff;border-radius:6px;padding:0 8px;margin-right:6px;font-size:13px}
:root[data-theme="dark"] .chunk h4 .n{color:#0d1220}
.struct{font-family:inherit;background:var(--soft);border-left:4px solid var(--brand-2);padding:6px 10px;border-radius:4px;margin:6px 0}
.struct b{background:var(--key);padding:0 4px;border-radius:4px}
.interp{margin:6px 0}
.check{background:var(--check);border:1px solid var(--check-line);border-radius:8px;padding:8px 12px;margin:8px 0}
.check:before{content:"CHECK";font-weight:800;font-size:12px;color:var(--accent);margin-right:8px}
.red{color:var(--red);font-weight:800}
.answer{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px 22px}
.answer h2{font-size:18px;color:var(--brand);border-bottom:2px solid var(--brand);padding-bottom:4px;margin-top:22px}
.answer h2:first-child{margin-top:0}
.answer h3{font-size:16px;margin-top:14px}
.answer h4{font-size:15px;margin:10px 0 4px}
.answer ul,.chunk ul{margin:4px 0;padding-left:22px}
.answer ul ul{list-style:"· "}
.concl{color:var(--red);font-weight:800;margin:8px 0}
.flow{display:flex;gap:6px;align-items:stretch;flex-wrap:wrap;margin:10px 0}
.flow .st{flex:1 1 120px;border:1.5px solid var(--brand-2);border-radius:8px;padding:6px 8px;text-align:center;background:var(--key)}
.flow .st b{display:block}
.flow .st span{font-size:12.5px;color:var(--sub)}
.flow .ar{align-self:center;color:var(--brand-2);font-weight:800}
.math{overflow-x:auto;overflow-y:hidden;margin:8px 0;text-align:center}
figure{margin:12px auto;text-align:center}
figure img{max-width:100%;height:auto;border:1px solid var(--line);border-radius:6px;background:#fff;cursor:zoom-in}
figcaption{font-size:13px;color:var(--sub);margin-top:4px}
.end{text-align:center;font-weight:700;margin-top:16px;color:var(--sub)}
.lightbox{position:fixed;inset:0;background:rgba(0,0,0,.8);display:flex;align-items:center;justify-content:center;z-index:50;padding:16px;cursor:zoom-out}
.lightbox img{max-width:100%;max-height:100%;background:#fff;border-radius:6px}
.keys td:last-child{font-size:13.5px}
.kw{display:inline-block;border:1px solid var(--line);border-radius:6px;padding:1px 7px;margin:2px;font-size:13px;background:var(--panel)}
.kw.hit{border-color:var(--ok);background:#e6f6ea;color:#1d6b2f}
.kw.miss{border-color:#f1b0b0;background:#fdeeee;color:#a61e1e}
:root[data-theme="dark"] .kw.hit{background:#163322;color:#8fe0a4}:root[data-theme="dark"] .kw.miss{background:#3a1c1c;color:#ff9b9b}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) .kw.hit{background:#163322;color:#8fe0a4}:root:not([data-theme="light"]) .kw.miss{background:#3a1c1c;color:#ff9b9b}}
.rate{display:flex;gap:6px;flex-wrap:wrap}
.rate button{border:1px solid var(--line);background:var(--panel);border-radius:8px;padding:6px 12px;cursor:pointer;font-weight:600}
.rate button.on.r1{background:var(--bad);color:#fff;border-color:var(--bad)}
.rate button.on.r2{background:var(--warn);color:#1b1f27;border-color:var(--warn)}
.rate button.on.r3{background:var(--ok);color:#fff;border-color:var(--ok)}
.pager{display:flex;justify-content:space-between;gap:8px;margin-top:14px}

/* practice */
.timer{font-family:ui-monospace,Consolas,monospace;font-size:22px;font-weight:800}
.timer.over{color:var(--bad)}
textarea.sheet{width:100%;min-height:340px;border:1px solid var(--line);border-radius:8px;padding:12px;background:
  repeating-linear-gradient(var(--panel),var(--panel) 27px,var(--line) 28px);line-height:28px;resize:vertical}
.split{display:grid;grid-template-columns:1fr 1fr;gap:14px}
@media (max-width:820px){.split{grid-template-columns:1fr}}
.meter{height:10px;background:var(--soft);border-radius:99px;overflow:hidden}
.meter i{display:block;height:100%;background:var(--ok)}
.exam-q{border:1px solid var(--line);border-radius:8px;padding:8px 12px;margin-bottom:8px;display:flex;gap:10px;align-items:flex-start;background:var(--panel)}
.exam-q.sel{border-color:var(--brand-2);background:var(--key)}

/* flash cards */
.flash{min-height:230px;display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;padding:26px;font-size:17px;cursor:pointer}
.flash .big{font-size:22px;font-weight:800;margin-bottom:6px}
.flash .back{font-size:15px;text-align:left;width:100%}

/* terms */
.term{border-bottom:1px solid var(--line);padding:10px 2px}
.term summary{cursor:pointer;list-style:none;display:flex;gap:8px;align-items:baseline;flex-wrap:wrap}
.term summary::-webkit-details-marker{display:none}
.term .nm{font-weight:800}
.term .en{font-size:13px;color:var(--sub)}
.stars{color:#e8a300;font-size:13px;letter-spacing:-1px}
.tdl{display:grid;grid-template-columns:72px 1fr;gap:4px 10px;margin:8px 0 2px;font-size:14px}
.tdl dt{font-weight:700;color:var(--brand)}
.tdl dd{margin:0;white-space:pre-line}

/* heat map */
.heat{display:grid;grid-template-columns:repeat(auto-fill,minmax(54px,1fr));gap:5px}
.heat a{display:block;text-align:center;font-size:11.5px;padding:7px 0;border-radius:6px;background:var(--soft);color:var(--sub);font-family:ui-monospace,Consolas,monospace}
.heat a.r1{background:var(--bad);color:#fff}.heat a.r2{background:var(--warn);color:#1b1f27}.heat a.r3{background:var(--ok);color:#fff}
.legend{display:flex;gap:12px;font-size:13px;color:var(--sub);flex-wrap:wrap}
.legend span:before{content:"";display:inline-block;width:10px;height:10px;border-radius:3px;margin-right:4px;vertical-align:-1px;background:var(--c)}
.hl{background:#fff1a8;color:#1b1f27;border-radius:3px}
footer{border-top:1px solid var(--line);padding:18px 0 30px;color:var(--sub);font-size:13px}
@media (max-width:600px){
  body{font-size:14.5px}
  .card{padding:14px}
  .answer{padding:14px}
  .search input{width:150px}
}
@media print{header,footer,.subtabs,.pager,.rate,.noprint{display:none!important}.card,.answer{box-shadow:none;border:0}}

/* 용어 그림 · 해설 슬라이드 */
.timg{display:flex;flex-wrap:wrap;gap:8px;margin:8px 0}
.timg img{max-width:100%;height:auto;border-radius:6px;background:#fff;border:1px solid var(--line)}
.timg img.fig{max-height:300px}
.timg.eqs{margin:6px 0 0}
.timg.eqs img{border:0;max-height:120px}
.flash .timg{justify-content:center}
.deckbar{margin-bottom:10px}
.deckbar select{flex:1;min-width:0;max-width:100%}
.slide{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);min-height:200px;display:flex;align-items:center;justify-content:center;overflow:hidden}
.slide img{display:block;width:100%;height:auto;max-height:100%;object-fit:contain;background:#fff}
.slide:fullscreen{background:#000;border:0;border-radius:0}