/* 레이아웃: 왼쪽 목차 레일 + 오른쪽 실험대(설명 → 그림 → 전개). 모눈종이 위의 색 펜 세 자루. */
:root {
  --bg: #f3f5f9;
  --panel: #ffffff;
  --canvas: #fbfcfe;
  --ink: #162033;
  --muted: #5a6478;
  --line: #d8deea;
  --grid: #e4e9f2;
  --axis: #9aa5ba;
  --accent: #3446c9;      /* 결과·선택 */
  --e1: #d9480f;          /* 첫째 열 / 첫째 벡터 */
  --e2: #0b8574;          /* 둘째 열 / 둘째 벡터 */
  --e3: #8e2fb0;          /* 셋째 */
  --warn: #c2255c;
  --ok: #2b8a3e;
  --hl: rgba(52, 70, 201, .12);
  --hl1: rgba(217, 72, 15, .14);
  --hl2: rgba(11, 133, 116, .14);
  --code: #eef1f7;
  --f-body: "IBM Plex Sans KR", "Apple SD Gothic Neo", "Malgun Gothic", system-ui, sans-serif;
  --f-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --f-math: "STIX Two Text", "Times New Roman", serif;
  --r: 10px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e131d; --panel: #151c29; --canvas: #121925; --ink: #e5e9f1; --muted: #98a2b6; --line: #29334a;
    --grid: #1f2838; --axis: #4d5a73; --accent: #8d9bff; --e1: #ff8f57; --e2: #3fd5bd; --e3: #d391ff;
    --warn: #ff6b9a; --ok: #6bd982; --hl: rgba(141, 155, 255, .16); --hl1: rgba(255, 143, 87, .17); --hl2: rgba(63, 213, 189, .16);
    --code: #1b2333; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0e131d; --panel: #151c29; --canvas: #121925; --ink: #e5e9f1; --muted: #98a2b6; --line: #29334a;
  --grid: #1f2838; --axis: #4d5a73; --accent: #8d9bff; --e1: #ff8f57; --e2: #3fd5bd; --e3: #d391ff;
  --warn: #ff6b9a; --ok: #6bd982; --hl: rgba(141, 155, 255, .16); --hl1: rgba(255, 143, 87, .17); --hl2: rgba(63, 213, 189, .16);
  --code: #1b2333; color-scheme: dark;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { margin: 0; }
body { background: var(--bg); color: var(--ink); font: 15px/1.7 var(--f-body); -webkit-font-smoothing: antialiased; }
a { color: var(--accent); }
button, input, select { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
code { font-family: var(--f-mono); font-size: .9em; background: var(--code); padding: 1px 5px; border-radius: 4px; }

/* ---------- 골격 */
.app { display: grid; grid-template-columns: 272px minmax(0, 1fr); min-height: 100vh; }
.nav { position: sticky; top: env(safe-area-inset-top, 0px); align-self: start; height: 100vh; overflow-y: auto; border-right: 1px solid var(--line); background: var(--panel); padding: 22px 18px 40px; }
.brand { display: block; text-decoration: none; color: var(--ink); font-weight: 700; font-size: 18px; letter-spacing: -.01em; line-height: 1.25; }
.brand small { display: block; font-weight: 400; font-size: 12px; color: var(--muted); letter-spacing: .02em; margin-top: 4px; }
.brand .mark { font-family: var(--f-math); font-style: italic; color: var(--accent); font-weight: 600; }
.navtoggle { display: none; }
#toc { margin-top: 22px; display: grid; gap: 14px; }
.toc-ch { display: grid; gap: 1px; }
.toc-ch h3 { margin: 0 0 4px; font-size: 11.5px; font-weight: 600; letter-spacing: .06em; color: var(--muted); display: flex; gap: 8px; align-items: baseline; }
.toc-ch h3 .no { font-family: var(--f-math); font-size: 15px; color: var(--ink); letter-spacing: 0; }
.toc-ch a { text-decoration: none; color: var(--ink); font-size: 13.5px; padding: 5px 10px; border-radius: 6px; line-height: 1.35; }
.toc-ch a:hover { background: var(--hl); }
.toc-ch a[aria-current="page"] { background: var(--accent); color: var(--panel); }

main { min-width: 0; padding: 36px 40px 80px; }
.page { max-width: 1060px; margin: 0 auto; display: grid; gap: 28px; }

/* ---------- 머리 */
.eyebrow { font-size: 12px; font-weight: 600; letter-spacing: .08em; color: var(--muted); display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.eyebrow .chno { font-family: var(--f-math); font-size: 16px; color: var(--accent); letter-spacing: 0; }
h1 { font-size: clamp(26px, 3.4vw, 36px); line-height: 1.2; margin: 6px 0 10px; letter-spacing: -.02em; text-wrap: balance; }
h1 .en { display: block; font-size: 14px; font-weight: 400; color: var(--muted); letter-spacing: .01em; margin-top: 6px; font-family: var(--f-math); font-style: italic; }
h2 { font-size: 19px; margin: 0 0 10px; letter-spacing: -.01em; text-wrap: balance; }
h3 { font-size: 15.5px; margin: 0 0 8px; }
.lead { max-width: 68ch; margin: 0; color: var(--ink); }
p { margin: 0 0 10px; max-width: 72ch; }
.muted { color: var(--muted); }
.small { font-size: 13px; }

/* ---------- 블록 */
.concept { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 20px 22px; display: grid; gap: 12px; }
.concept ul { margin: 0; padding-left: 20px; display: grid; gap: 6px; }
.concept li { max-width: 72ch; }
.keyline { font-family: var(--f-math); font-size: 19px; padding: 10px 14px; border-left: 3px solid var(--accent); background: var(--hl); border-radius: 0 6px 6px 0; overflow-x: auto; line-height: 1.6; }
.keyline .lbl { font-family: var(--f-body); font-size: 12px; color: var(--muted); display: block; letter-spacing: .04em; }
.lab { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); gap: 20px; align-items: start; }
.lab.wide { grid-template-columns: minmax(0, 1fr); }
.lab > * { min-width: 0; }
.card { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 18px; display: grid; gap: 14px; min-width: 0; }
.card > h3 { display: flex; gap: 6px 10px; align-items: baseline; flex-wrap: wrap; margin: 0; }
.card > h3 small { margin-left: auto; }
.card > h3 small { font-weight: 400; color: var(--muted); font-size: 12.5px; }
.viz { border: 1px solid var(--line); border-radius: 8px; overflow: hidden; background: var(--canvas); position: relative; }
canvas.plane { display: block; width: 100%; }
.legend { display: flex; flex-wrap: wrap; gap: 6px 14px; font-size: 12.5px; color: var(--muted); }
.legend span { display: inline-flex; align-items: center; gap: 6px; }
.legend i { width: 14px; height: 3px; border-radius: 2px; display: inline-block; }
.row { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.row.top { align-items: flex-start; }
.scroll { overflow-x: auto; max-width: 100%; padding-bottom: 4px; }
.sep { height: 1px; background: var(--line); }

/* 전개 상자 */
.expand { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); }
.expand > summary { cursor: pointer; padding: 12px 18px; font-weight: 600; list-style: none; display: block; }
.expand > summary::-webkit-details-marker { display: none; }
.expand > summary::before { content: "+"; font-family: var(--f-mono); width: 20px; height: 20px; border: 1px solid var(--line); border-radius: 5px; display: inline-grid; place-items: center; font-size: 13px; color: var(--accent); margin-right: 10px; vertical-align: middle; }
.expand[open] > summary::before { content: "−"; }
.expand > .body { padding: 0 18px 18px; display: grid; gap: 12px; min-width: 0; overflow-x: auto; }
.math { font-family: var(--f-math); font-size: 17px; line-height: 1.9; }
.math .sum { font-size: 1.3em; }
.calc { font-family: var(--f-mono); font-size: 13.5px; line-height: 1.85; background: var(--code); border-radius: 8px; padding: 12px 14px; overflow-x: auto; white-space: nowrap; }
.calc .ln { display: block; }
.calc b, .lines b { color: var(--accent); }
.lines { display: grid; gap: 2px; margin-top: 8px; font-family: var(--f-mono); font-size: 13px; overflow-x: auto; }
.lines .ln { white-space: nowrap; }
.var { font-family: var(--f-math); font-style: italic; font-size: 1.08em; }
b.vec { font-family: var(--f-math); font-weight: 700; font-size: 1.06em; }
sub, sup { font-size: .72em; line-height: 0; }
.t1 { color: var(--e1); } .t2 { color: var(--e2); } .t3 { color: var(--e3); } .ta { color: var(--accent); } .tw { color: var(--warn); } .tok { color: var(--ok); }
.pill { display: inline-flex; align-items: center; gap: 6px; font-size: 12.5px; font-weight: 600; padding: 3px 10px; border-radius: 999px; border: 1px solid currentColor; }
.pill.ok { color: var(--ok); } .pill.bad { color: var(--warn); } .pill.info { color: var(--accent); }

/* ---------- 행렬 */
.mxw { display: inline-flex; align-items: center; gap: 8px; vertical-align: middle; font-family: var(--f-mono); }
.mxname { font-family: var(--f-math); font-style: italic; font-size: 20px; font-weight: 600; white-space: nowrap; }
.mxname sup, .mxname sub { font-style: normal; }
.mxeq { font-family: var(--f-math); font-size: 19px; }
.mx { display: inline-grid; position: relative; padding: 4px 9px; gap: 2px 4px; }
.mx::before, .mx::after { content: ""; position: absolute; top: 0; bottom: 0; width: 7px; border: 1.75px solid var(--ink); }
.mx::before { left: 0; border-right: 0; border-radius: 3px 0 0 3px; }
.mx::after { right: 0; border-left: 0; border-radius: 0 3px 3px 0; }
.mx.det::before, .mx.det::after { width: 0; border-radius: 0; }
.mx.det::after { border-left: 0; }
.mx .c { min-width: 38px; padding: 3px 7px; text-align: center; border-radius: 5px; font-size: 14px; line-height: 1.35; position: relative; font-variant-numeric: tabular-nums; transition: background .15s, opacity .15s; display: grid; place-items: center; }
.mx.has-ix .c { padding-top: 15px; min-width: 46px; }
.mx .c .ix { position: absolute; top: 1px; left: 0; right: 0; font-size: 9.5px; color: var(--muted); font-family: var(--f-math); font-style: italic; line-height: 1.2; }
.mx .c.aug { margin-left: 8px; }
.mx .c.aug::before { content: ""; position: absolute; left: -6px; top: 2px; bottom: 2px; border-left: 1.5px dashed var(--muted); }
.mx .c.hl { background: var(--hl); }
.mx .c.h1 { background: var(--hl1); }
.mx .c.h2 { background: var(--hl2); }
.mx .c.pv { background: var(--accent); color: var(--panel); font-weight: 600; }
.mx .c.pv .ix { color: var(--panel); opacity: .8; }
.mx .c.dim { opacity: .28; }
.mx .c.x { opacity: .3; text-decoration: line-through; }
.mx .c.k1 { color: var(--e1); font-weight: 600; } .mx .c.k2 { color: var(--e2); font-weight: 600; } .mx .c.k3 { color: var(--e3); font-weight: 600; }
.mx .c.changed { animation: flash .9s ease-out; }
@keyframes flash { from { background: var(--hl1); } to { background: transparent; } }
.mx.sm .c { min-width: 26px; padding: 1px 4px; font-size: 12px; }
.mx.sm { padding: 2px 7px; }
.fr { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; font-size: .82em; line-height: 1.05; }
.fr > span:first-child { border-bottom: 1px solid currentColor; padding: 0 2px; }
.mxrow { display: flex; flex-wrap: wrap; gap: 14px 18px; align-items: center; }
.op { font-family: var(--f-math); font-size: 22px; color: var(--muted); }

/* 편집기 */
.edwrap { display: grid; gap: 10px; }
.ed { display: flex; align-items: center; gap: 8px; overflow-x: auto; padding: 2px; }
.edmx input.c { width: 54px; min-width: 0; text-align: center; border: 1px solid var(--line); background: var(--canvas); border-radius: 6px; padding: 6px 2px; font-family: var(--f-mono); font-size: 14px; }
.edmx input.c:focus { border-color: var(--accent); outline: none; box-shadow: 0 0 0 3px var(--hl); }
.edmx input.c.bad { border-color: var(--warn); color: var(--warn); }
.edmx input.c.aug { margin-left: 10px; }
.edtools { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; font-size: 13px; }
.sz { display: inline-flex; align-items: center; gap: 6px; color: var(--muted); }
.sz b { color: var(--ink); font-family: var(--f-mono); font-weight: 500; min-width: 30px; text-align: center; }
.sz button { width: 26px; height: 26px; border: 1px solid var(--line); border-radius: 6px; background: var(--panel); cursor: pointer; line-height: 1; }
.presets { display: inline-flex; flex-wrap: wrap; gap: 6px; }
.hint { font-size: 12px; color: var(--muted); margin: 0; }

/* 버튼 */
.chip, .stepper button, .btn { border: 1px solid var(--line); background: var(--panel); border-radius: 999px; padding: 5px 13px; cursor: pointer; font-size: 13px; line-height: 1.3; }
.chip:hover, .stepper button:hover, .btn:hover { border-color: var(--accent); }
.chip.on, .chip[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--panel); }
.chip.ghost, .stepper .ghost { border-style: dashed; }
.stepper { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.stepper .primary, .btn.primary { background: var(--accent); color: var(--panel); border-color: var(--accent); }
.stepcount { font-family: var(--f-mono); font-size: 12.5px; color: var(--muted); min-width: 76px; text-align: center; }
.tabs { display: flex; gap: 4px; flex-wrap: wrap; border-bottom: 1px solid var(--line); }
.tabs button { border: 0; background: none; padding: 8px 12px; cursor: pointer; border-bottom: 2px solid transparent; margin-bottom: -1px; font-size: 14px; color: var(--muted); }
.tabs button[aria-selected="true"] { color: var(--ink); border-bottom-color: var(--accent); font-weight: 600; }
.sl { display: grid; grid-template-columns: 74px minmax(0, 1fr) 46px; gap: 10px; align-items: center; font-size: 13px; }
.sl-l { color: var(--muted); }
.sl input { width: 100%; accent-color: var(--accent); }
.sl output { font-family: var(--f-mono); font-size: 12.5px; text-align: right; }
.sliders { display: grid; gap: 6px; }
select { border: 1px solid var(--line); background: var(--panel); border-radius: 6px; padding: 4px 8px; font-size: 13px; }

/* 단계 설명 */
.stepbox { border-left: 3px solid var(--accent); padding: 4px 0 4px 14px; display: grid; gap: 6px; min-width: 0; }
.stepbox .op-t { font-family: var(--f-math); font-size: 18px; }
.stepbox .ph { font-size: 11.5px; font-weight: 600; letter-spacing: .06em; color: var(--accent); }
.steplist { list-style: none; margin: 0; padding: 0; display: grid; gap: 2px; font-size: 13px; max-height: 220px; overflow-y: auto; }
.steplist li { padding: 3px 8px; border-radius: 5px; cursor: pointer; display: flex; gap: 10px; }
.steplist li .n { font-family: var(--f-mono); color: var(--muted); min-width: 18px; }
.steplist li.cur { background: var(--hl); }

/* 표 */
table.t { border-collapse: collapse; font-size: 13.5px; width: 100%; }
table.t th, table.t td { border-bottom: 1px solid var(--line); padding: 7px 10px; text-align: left; vertical-align: top; }
table.t th { font-size: 12px; color: var(--muted); font-weight: 600; letter-spacing: .03em; }
table.t td.num { font-family: var(--f-mono); }

/* 막대 */
.bar { display: flex; height: 26px; border-radius: 6px; overflow: hidden; border: 1px solid var(--line); font-size: 12px; font-weight: 600; }
.bar > span { display: grid; place-items: center; color: var(--panel); white-space: nowrap; overflow: hidden; transition: flex-grow .3s; }

/* 항 카드 (여인수 전개) */
.terms { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; }
.term { border: 1px solid var(--line); border-radius: 8px; padding: 12px; display: grid; gap: 8px; background: var(--canvas); min-width: 0; }
.term:hover, .term.on { border-color: var(--accent); }
.term .tt { font-family: var(--f-math); font-size: 16px; }
.term .val { font-family: var(--f-mono); font-size: 13px; color: var(--muted); }
.term .val b { color: var(--accent); }

/* 홈 */
.hero { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 32px; align-items: center; }
.hero h1 { font-size: clamp(30px, 4.4vw, 46px); }
.hero h1 em { font-style: normal; color: var(--accent); }
.legendbox { display: grid; gap: 8px; font-size: 13.5px; }
.legendbox div { display: flex; gap: 10px; align-items: center; }
.sw { width: 18px; height: 18px; border-radius: 4px; flex: none; }
.chgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(290px, 1fr)); gap: 14px; }
.chcard { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 18px; display: grid; gap: 8px; align-content: start; }
.chcard h3 { display: flex; gap: 10px; align-items: baseline; margin: 0; }
.chcard h3 .no { font-family: var(--f-math); font-size: 26px; color: var(--accent); line-height: 1; }
.chcard ul { margin: 0; padding: 0; list-style: none; display: grid; gap: 2px; }
.chcard a { text-decoration: none; color: var(--ink); font-size: 14px; display: flex; justify-content: space-between; gap: 8px; padding: 4px 0; border-bottom: 1px dashed var(--line); }
.chcard a:hover { color: var(--accent); }
.chcard a span { color: var(--muted); font-size: 12px; }

.pager { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; border-top: 1px solid var(--line); padding-top: 18px; }
.pager a { text-decoration: none; display: grid; gap: 2px; padding: 10px 14px; border: 1px solid var(--line); border-radius: 8px; background: var(--panel); color: var(--ink); max-width: 48%; }
.pager a small { color: var(--muted); font-size: 12px; }
.pager a.next { text-align: right; margin-left: auto; }
.pager a:hover { border-color: var(--accent); }

/* 공리 표 */
.ax { display: grid; gap: 6px; }
.ax button { text-align: left; border: 1px solid var(--line); background: var(--canvas); border-radius: 8px; padding: 8px 12px; cursor: pointer; display: grid; grid-template-columns: 26px minmax(0, 1fr) auto; gap: 10px; align-items: center; font-size: 13.5px; }
.ax button.on { border-color: var(--accent); background: var(--hl); }
.ax .no { font-family: var(--f-mono); color: var(--muted); }
.ax .st { font-weight: 700; font-size: 12px; }

@media (max-width: 980px) {
  .lab, .hero { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 820px) {
  .app { grid-template-columns: minmax(0, 1fr); }
  .nav { position: sticky; top: env(safe-area-inset-top, 0px); height: auto; max-height: 100vh; z-index: 5; padding: 12px 16px; border-right: 0; border-bottom: 1px solid var(--line); display: grid; grid-template-columns: 1fr auto; align-items: center; }
  .brand small { display: none; }
  .navtoggle { display: inline-block; border: 1px solid var(--line); background: var(--panel); border-radius: 999px; padding: 5px 14px; cursor: pointer; font-size: 13px; }
  #toc { grid-column: 1 / -1; display: none; max-height: 70vh; overflow-y: auto; margin-top: 12px; }
  .nav.open #toc { display: grid; }
  main { padding: 24px 16px 60px; }
  .pager a { max-width: 100%; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }
.page, .card, .concept, .expand > .body { grid-template-columns: minmax(0, 1fr); }
.mxrow > * { max-width: 100%; }

.en-term { font-size: .8em; font-weight: 400; font-style: normal; color: var(--muted); margin-left: 2px; letter-spacing: 0; }
.hide-en .en-term { display: none; }
.chcard a .t-ko { color: inherit; font-size: 14px; display: grid; }
.chcard a .t-ko small { margin: 0; font-size: 11.5px; }

.views { display: flex; gap: 12px; margin-top: 10px; font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.views b { color: var(--ink); font-weight: 600; font-family: var(--f-mono); }
@media (max-width: 820px) { .views { grid-column: 1 / -1; grid-row: 2; margin-top: 4px; } .navtoggle { grid-column: 2; grid-row: 1; } }