/* 원래 Sadiku 문제 카드의 모눈 패드 디자인을 그대로 잇는다: 왼쪽 장 목록, 오른쪽에 문제 한 장 */
:root {
  --bg: #EDF0EE; --panel: #FFFFFF; --ink: #16232E; --muted: #5D6A70; --line: #D5DCD8;
  --accent: #0E7C66; --accent-soft: #DCEFE9; --warn: #B4531A; --warn-soft: #F7E6DA;
  --bad: #C2402F; --bad-soft: #F8E1DD;
  --paper: #FFFFFF; --chip: #F4F6F5; --grid: #E3ECE8;
  --f-body: "IBM Plex Sans KR", -apple-system, "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, Menlo, Consolas, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0F1517; --panel: #172024; --ink: #E3EAE8; --muted: #93A19F; --line: #2A3639;
    --accent: #3CC9A6; --accent-soft: #163A33; --warn: #F0965C; --warn-soft: #3A2618;
    --bad: #F07A6A; --bad-soft: #3B1D19;
    --chip: #1E292C; color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg); color: var(--ink);
  font-family: var(--f-body); font-size: 15px; line-height: 1.6;
  padding: max(20px, env(safe-area-inset-top)) max(16px, env(safe-area-inset-right)) max(48px, env(safe-area-inset-bottom)) max(16px, env(safe-area-inset-left));
}
button { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.wrap { max-width: 1180px; margin: 0 auto; display: grid; grid-template-columns: 250px minmax(0, 1fr); gap: 24px; align-items: start; }

header.top { grid-column: 1 / -1; display: flex; flex-wrap: wrap; align-items: center; gap: 6px 16px; }
header.top h1 { font-size: 1.35rem; margin: 0; font-weight: 700; letter-spacing: -.01em; }
header.top .sub { color: var(--muted); font-size: .9rem; }
.topspace { flex: 1; }
.modes { display: inline-flex; background: var(--chip); border: 1px solid var(--line); border-radius: 9px; padding: 3px; gap: 2px; }
.modes a { text-decoration: none; color: var(--muted); padding: 4px 14px; border-radius: 7px; font-size: .9rem; font-weight: 600; }
.modes a[aria-current="page"] { background: var(--panel); color: var(--ink); box-shadow: 0 1px 2px rgba(0, 0, 0, .08); }
.offline { font-size: .78rem; color: var(--muted); font-family: var(--f-mono); }
.offline.ready { color: var(--accent); }

.menu { position: relative; }
.menu summary { list-style: none; padding: 4px 12px; }
.menu summary::-webkit-details-marker { display: none; }
.menu-pop { position: absolute; right: 0; top: calc(100% + 6px); z-index: 20; background: var(--panel); border: 1px solid var(--line); border-radius: 10px; box-shadow: 0 8px 24px rgba(0, 0, 0, .12); padding: 6px; min-width: 210px; display: flex; flex-direction: column; }
.menu-item { display: block; text-align: left; border: 0; background: none; padding: 8px 10px; border-radius: 7px; cursor: pointer; font-size: .9rem; }
.menu-item:hover { background: var(--chip); }

/* 장 목록 */
nav.rail { position: sticky; top: max(12px, env(safe-area-inset-top)); display: flex; flex-direction: column; gap: 2px; max-height: calc(100vh - 40px); overflow: auto; }
.rail-sub { font-size: .72rem; letter-spacing: .06em; color: var(--muted); font-weight: 600; padding: 14px 10px 4px; }
.ch { display: grid; grid-template-columns: 2.2em minmax(0, 1fr); gap: 2px 8px; text-align: left; border: 0; background: none; padding: 8px 10px; border-radius: 8px; cursor: pointer; }
.ch:hover { background: var(--chip); }
.ch[aria-current="true"] { background: var(--panel); box-shadow: 0 0 0 1px var(--line); }
.ch .no { font-family: var(--f-mono); font-weight: 600; color: var(--accent); grid-row: span 2; }
.ch.special .no { color: var(--warn); }
.ch .t { font-weight: 600; font-size: .92rem; line-height: 1.3; }
.ch .meta { font-size: .75rem; color: var(--muted); display: flex; gap: 6px; align-items: center; }
.bar { height: 3px; background: var(--line); border-radius: 2px; flex: 1; overflow: hidden; max-width: 80px; display: flex; }
.bar i { display: block; height: 100%; }
.bar i.ok { background: var(--accent); }
.bar i.mid { background: var(--warn); }
.bar i.bad { background: var(--bad); }
.chsel { display: none; }

main { min-width: 0; display: flex; flex-direction: column; gap: 14px; }
.controls { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; }
.ctitle { font-weight: 700; font-size: 1.05rem; }
.seg { display: inline-flex; background: var(--chip); border: 1px solid var(--line); border-radius: 9px; padding: 3px; gap: 2px; flex-wrap: wrap; }
.seg button { border: 0; background: none; padding: 5px 12px; border-radius: 7px; cursor: pointer; font-size: .88rem; color: var(--muted); white-space: nowrap; }
.seg button[aria-pressed="true"] { background: var(--panel); color: var(--ink); font-weight: 600; box-shadow: 0 1px 2px rgba(0, 0, 0, .08); }

/* 문제 번호 */
.grid { display: flex; flex-wrap: wrap; gap: 5px; }
.num { font-family: var(--f-mono); font-size: .78rem; min-width: 3.4em; padding: 4px 6px; border: 1px solid var(--line); background: var(--panel); border-radius: 6px; cursor: pointer; font-variant-numeric: tabular-nums; }
.num.g3 { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }
.num.g2 { background: var(--warn-soft); border-color: var(--warn); color: var(--warn); }
.num.g1 { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }
.num[aria-current="true"] { outline: 2px solid var(--ink); outline-offset: 1px; }

/* 문제 카드 */
.card { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; overflow: hidden; }
.card-h { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 10px; padding: 14px 18px; border-bottom: 1px solid var(--line); }
.card-h .lab { font-family: var(--f-mono); font-weight: 600; font-size: 1.05rem; margin-right: 4px; }
.tag { font-size: .72rem; letter-spacing: .02em; padding: 2px 7px; border-radius: 5px; background: var(--chip); color: var(--muted); border: 1px solid var(--line); }
.tag.due.g1 { color: var(--bad); border-color: var(--bad); }
.tag.due.g2 { color: var(--warn); border-color: var(--warn); }
.tag.due.g3 { color: var(--accent); border-color: var(--accent); }
.card-h .pos { margin-left: auto; color: var(--muted); font-size: .82rem; font-family: var(--f-mono); }

.scan { background: var(--paper); padding: 14px 10px; display: flex; justify-content: center; }
.scan img { display: block; width: 100%; max-width: 760px; height: auto; }
/* 미적분: 수식으로 된 문제 */
.texq { background: var(--paper); padding: 30px 18px; font-size: 1.25rem; text-align: center; overflow-x: auto; }
.qnote { font-size: .85rem; color: var(--muted); margin-top: 10px; }
.reveal.hint-box { background: var(--chip); }
.steps { margin: 0; padding-left: 1.4em; }
.steps li { margin: .5em 0; }
.answer.tex { font-size: 1.1rem; }

.actions { display: flex; flex-wrap: wrap; gap: 8px; padding: 12px 18px; border-top: 1px solid var(--line); }
.btn { border: 1px solid var(--line); background: var(--chip); padding: 7px 14px; border-radius: 8px; cursor: pointer; font-size: .9rem; }
.btn.pri { background: var(--accent); border-color: var(--accent); color: var(--panel); font-weight: 600; }
.btn.g-btn.ok[aria-pressed="true"] { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); font-weight: 600; }
.btn.g-btn.mid[aria-pressed="true"] { background: var(--warn-soft); border-color: var(--warn); color: var(--warn); font-weight: 600; }
.btn.g-btn.bad[aria-pressed="true"] { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); font-weight: 600; }
.spacer { flex: 1; }

.reveal { padding: 16px 20px; border-top: 1px solid var(--line); display: flex; flex-direction: column; gap: 10px; }
.reveal h3 { margin: 0; font-size: .75rem; letter-spacing: .08em; color: var(--muted); font-weight: 600; }
.answer { font-size: 1rem; font-weight: 500; overflow-x: auto; }
.answer p { margin: .3em 0; }
.sol { max-width: 72ch; overflow-x: auto; }
.sol p { margin: .5em 0; }
.sol ol, .sol ul { margin: .4em 0; padding-left: 1.4em; }
.sol li { margin: .2em 0; }
.sol strong { color: var(--accent); font-weight: 600; }
.katex-display { overflow-x: auto; overflow-y: hidden; max-width: 100%; padding: 2px 0; }
.ansimg { max-width: 100%; background: #fff; border-radius: 6px; }

.nav { display: flex; gap: 8px; justify-content: space-between; align-items: center; }
.hint { color: var(--muted); font-size: .78rem; text-align: center; }
.empty { padding: 40px 20px; text-align: center; color: var(--muted); }


@media (max-width: 820px) {
  .wrap { grid-template-columns: minmax(0, 1fr); }
  nav.rail { display: none; }
  .chsel { display: block; width: 100%; padding: 8px 10px; border-radius: 8px; border: 1px solid var(--line); background: var(--panel); color: var(--ink); font: inherit; }
  .scan { padding: 8px 4px; }
  .hint { display: none; }
}
@media (prefers-reduced-motion: no-preference) {
  .reveal { animation: in .18s ease-out; }
  @keyframes in { from { opacity: .4; transform: translateY(-3px); } to { opacity: 1; } }
}