:root {
  --bg: #f6f7fb;
  --card: #ffffff;
  --ink: #1d2433;
  --muted: #5d6b82;
  --line: #dde2ee;
  --brand: #2f6fed;
  --brand-ink: #ffffff;
  --brand-soft: #e8f0ff;
  --ok: #1f9d55;
  --ok-soft: #e3f6ea;
  --bad: #d64545;
  --bad-soft: #fde8e8;
  --warn-soft: #fff6dd;
  --warn-line: #f0c75a;
  --code-bg: #f1f4fa;
  --blue: #cfe0ff;
  --green: #cdeec5;
  --orange: #ffd2b3;
  --screen: #fbf8ff;
  --mbtn: #6750a4;
  --radius: 12px;
}
:root[data-theme="dark"] {
  --bg: #0f1420;
  --card: #171e2e;
  --ink: #e6ebf5;
  --muted: #98a6c0;
  --line: #2a3550;
  --brand: #6b9bff;
  --brand-ink: #0b1220;
  --brand-soft: #1d2a4a;
  --ok: #54d08a;
  --ok-soft: #14301f;
  --bad: #ff7a7a;
  --bad-soft: #3a1b1b;
  --warn-soft: #34290d;
  --warn-line: #8a6d1a;
  --code-bg: #0e1424;
  --blue: #27407a;
  --green: #285a2b;
  --orange: #6b3d1c;
  --screen: #1c2335;
  --mbtn: #7c66c9;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f1420;
    --card: #171e2e;
    --ink: #e6ebf5;
    --muted: #98a6c0;
    --line: #2a3550;
    --brand: #6b9bff;
    --brand-ink: #0b1220;
    --brand-soft: #1d2a4a;
    --ok: #54d08a;
    --ok-soft: #14301f;
    --bad: #ff7a7a;
    --bad-soft: #3a1b1b;
    --warn-soft: #34290d;
    --warn-line: #8a6d1a;
    --code-bg: #0e1424;
    --blue: #27407a;
    --green: #285a2b;
    --orange: #6b3d1c;
    --screen: #1c2335;
    --mbtn: #7c66c9;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Pretendard", "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans KR", system-ui, sans-serif;
  line-height: 1.65;
  font-size: 16px;
  word-break: keep-all;
  overflow-wrap: break-word;
}
code, pre { font-family: "JetBrains Mono", "D2Coding", Consolas, "Courier New", monospace; }
code { background: var(--code-bg); padding: 1px 5px; border-radius: 4px; font-size: 0.9em; word-break: break-word; }

.top {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 90%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.top-inner { max-width: 880px; margin: 0 auto; padding: 10px 16px 0; }
.top-row { display: flex; align-items: center; justify-content: space-between; gap: 8px; }
h1 { font-size: 18px; margin: 0; letter-spacing: -0.02em; }
h1 small { color: var(--muted); font-weight: 500; font-size: 12px; margin-left: 6px; white-space: nowrap; }
@media (max-width: 420px) { h1 small { display: none; } }
.tools { display: flex; gap: 6px; }
.tools a, .tools button {
  border: 1px solid var(--line); background: var(--card); color: var(--ink);
  padding: 6px 10px; border-radius: 8px; font-size: 13px; cursor: pointer; text-decoration: none; font-family: inherit;
}
.tabs { display: flex; gap: 2px; margin-top: 8px; overflow-x: auto; scrollbar-width: none; }
.tabs::-webkit-scrollbar { display: none; }
.tab {
  border: 0; background: none; color: var(--muted); padding: 10px 14px; font-size: 15px; font-weight: 600;
  border-bottom: 3px solid transparent; cursor: pointer; white-space: nowrap; font-family: inherit;
  display: inline-flex; align-items: center; gap: 6px;
}
.tab svg { width: 18px; height: 18px; flex: none; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }
.tab[aria-selected="true"] { color: var(--brand); border-bottom-color: var(--brand); }

main { max-width: 880px; margin: 0 auto; padding: 16px; }
.panel[hidden] { display: none; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  margin: 0 0 14px; overflow: hidden;
}
.card > summary, .card-head {
  list-style: none; cursor: pointer; padding: 14px 16px; display: flex; gap: 10px; align-items: flex-start; justify-content: space-between;
}
.card > summary::-webkit-details-marker { display: none; }
.card h3 { margin: 0; font-size: 17px; letter-spacing: -0.01em; }
.card .src { color: var(--muted); font-size: 12.5px; margin-top: 2px; }
.chev { transition: transform 0.15s; color: var(--muted); flex: none; margin-top: 3px; }
details[open] > summary .chev { transform: rotate(90deg); }
.card-body { padding: 2px 16px 16px; border-top: 1px solid var(--line); }

h4 { margin: 20px 0 8px; font-size: 15px; color: var(--brand); }
ul, ol { padding-left: 22px; margin: 6px 0; }
li { margin: 4px 0; }

.tbl-wrap { overflow-x: auto; margin: 8px 0; border: 1px solid var(--line); border-radius: 8px; }
table { border-collapse: collapse; width: 100%; font-size: 14.5px; }
th, td { padding: 8px 10px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--line); }
th { background: var(--brand-soft); font-weight: 600; white-space: nowrap; }
tr:last-child td { border-bottom: 0; }

.tip { background: var(--warn-soft); border: 1px solid var(--warn-line); border-radius: 8px; padding: 10px 12px; margin: 14px 0 4px; font-size: 14.5px; }
.steps { counter-reset: s; list-style: none; padding-left: 0; }
.steps li { counter-increment: s; position: relative; padding-left: 34px; }
.steps li::before {
  content: counter(s); position: absolute; left: 0; top: 1px; width: 24px; height: 24px; border-radius: 50%;
  background: var(--brand); color: var(--brand-ink); font-size: 13px; font-weight: 700; display: grid; place-items: center;
}

.codeblock { border: 1px solid var(--line); border-radius: 8px; margin: 10px 0; overflow: hidden; }
.code-title { display: flex; justify-content: space-between; padding: 6px 12px; background: var(--brand-soft); font-size: 13px; font-weight: 600; }
.code-title span { color: var(--muted); font-weight: 500; }
pre { margin: 0; padding: 12px; background: var(--code-bg); overflow-x: auto; font-size: 13px; line-height: 1.55; }
pre code { background: none; padding: 0; font-size: inherit; word-break: normal; }
.notes { margin: 0; padding: 4px 12px 10px; font-size: 14px; }
.notes > div { display: grid; grid-template-columns: minmax(0, 40%) 1fr; gap: 4px 12px; padding: 6px 0; border-top: 1px dashed var(--line); }
.notes dt, .notes dd { margin: 0; }
.notes dt code { background: none; padding: 0; color: var(--brand); font-weight: 600; }
@media (max-width: 560px) { .notes > div { grid-template-columns: 1fr; } }

.diagram { margin: 14px 0 6px; }
.fig-n { display: none; }
svg.dg { display: block; width: 100%; height: auto; margin: 0 auto; }
.fig-w svg.lc { max-width: 600px; }
.fig-n svg.dg { max-width: 440px; }
figcaption { font-size: 13.5px; color: var(--muted); margin-top: 6px; line-height: 1.55; }
@media (max-width: 640px) {
  .fig-w { display: none; }
  .fig-n { display: block; }
}

/* 그림 공통 */
.d-line { fill: none; stroke: var(--muted); stroke-width: 1.4; }
.d-acc { fill: none; stroke: var(--brand); stroke-width: 1.8; }
.d-badl { fill: none; stroke: var(--bad); stroke-width: 1.6; }
.d-okl { fill: none; stroke: var(--ok); stroke-width: 1.8; }
.d-dash { stroke-dasharray: 5 4; }
.d-head { fill: var(--muted); }
.d-head-acc { fill: var(--brand); }
.d-head-bad { fill: var(--bad); }
.d-head-ok { fill: var(--ok); }
.d-acc-fill { fill: var(--brand); }
.d-box { fill: var(--card); stroke: var(--muted); stroke-width: 1.2; }
.d-soft { fill: var(--brand-soft); stroke: var(--brand); stroke-width: 1.2; }
.d-box-a { fill: var(--blue); stroke: var(--brand); stroke-width: 1.1; }
.d-box-b { fill: var(--green); stroke: var(--ok); stroke-width: 1.1; }
.d-ghost { fill: none; stroke: var(--muted); stroke-width: 1.1; stroke-dasharray: 4 3; }
.d-faded { opacity: 0.75; }
.d-hl { fill: var(--blue); opacity: 0.55; }
.d-hl2 { fill: var(--green); opacity: 0.55; }
.d-frame { fill: var(--screen); stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 5 4; }
.d-phone { fill: var(--screen); stroke: var(--ink); stroke-width: 2; }
.d-notch { stroke: var(--ink); stroke-width: 3; stroke-linecap: round; }
.d-field { fill: var(--card); stroke: var(--muted); stroke-width: 1; }
.d-lin1 { fill: none; stroke: var(--brand); stroke-width: 1.5; stroke-dasharray: 6 3; }
.d-lin2 { fill: none; stroke: var(--ok); stroke-width: 1.5; stroke-dasharray: 6 3; }
.d-mbtn { fill: var(--mbtn); }
.d-mbtn-t { fill: #fff; font-size: 10px; font-weight: 600; }
.d-xs { font-size: 8.6px; }
.d-gray { fill: #bdbdbd; }
.d-gray-t { fill: #1d2433; font-size: 13px; }
.d-num circle { fill: var(--brand); }
.d-num-t { fill: var(--brand-ink); font-size: 10.5px; font-weight: 700; }
.d-t { fill: var(--ink); font-size: 12.5px; }
.d-b { font-weight: 700; }
.d-big { font-size: 16px; }
.d-s { fill: var(--muted); font-size: 11px; }
.d-m { fill: var(--ink); font-family: Consolas, "D2Coding", monospace; font-size: 11px; white-space: pre; }
text.d-acc-t { fill: var(--brand); }
text.d-bad-t { fill: var(--bad); }
text.d-ok-t { fill: var(--ok); }

/* 생명주기 흐름도 + 시뮬레이터 */
.lc-box { fill: var(--card); stroke: var(--muted); stroke-width: 1.2; transition: fill 0.25s, stroke 0.25s; }
.lc-blue { fill: var(--blue); stroke: var(--brand); stroke-width: 1.2; transition: fill 0.25s; }
.lc-green { fill: var(--green); stroke: var(--ok); stroke-width: 1.2; transition: fill 0.25s; }
.lc-orange { fill: var(--orange); stroke: #d9822b; stroke-width: 1.2; transition: fill 0.25s; }
.lc-fn { fill: var(--ink); font-family: Consolas, monospace; font-size: 12.5px; }
.lc-state { fill: var(--ink); font-size: 12.5px; font-weight: 600; }
.lc [data-fn].lit rect, .lc [data-fn].lit ellipse { fill: var(--brand); stroke: var(--brand); }
.lc [data-fn].lit text { fill: var(--brand-ink); font-weight: 700; }
.lc [data-fn].now ellipse { stroke: var(--brand); stroke-width: 3.5; }
.lc-sim { margin-top: 10px; padding: 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--bg); }
.lc-sim:empty { display: none; }
.sim-head { display: flex; flex-wrap: wrap; gap: 4px 12px; align-items: baseline; font-size: 14px; }
.sim-state { color: var(--muted); font-size: 13.5px; }
.sim-btns { display: flex; flex-wrap: wrap; gap: 6px; margin: 10px 0 8px; }
.sim-btns .chip { font-size: 13px; padding: 6px 10px; }
.sim-btns .chip:disabled { opacity: 0.4; cursor: not-allowed; }
.sim-log { min-height: 24px; font-size: 14px; }
.sim-act { font-weight: 700; margin-right: 4px; }
.sim-none { color: var(--bad); font-size: 13px; }

/* 퀴즈 */
.bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 12px; }
select, .chip, .btn, textarea {
  font-family: inherit; font-size: 14px; color: var(--ink); background: var(--card);
  border: 1px solid var(--line); border-radius: 8px;
}
select { padding: 8px 10px; max-width: 100%; min-width: 0; text-overflow: ellipsis; }
.chip { padding: 7px 12px; cursor: pointer; }
.chip[aria-pressed="true"] { background: var(--brand); color: var(--brand-ink); border-color: var(--brand); }
.btn { padding: 8px 14px; cursor: pointer; font-weight: 600; }
.btn.primary { background: var(--brand); color: var(--brand-ink); border-color: var(--brand); }
.btn.ok { background: var(--ok-soft); border-color: var(--ok); color: var(--ok); }
.btn.bad { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }
.btn.on { outline: 2px solid currentColor; }
.stats { color: var(--muted); font-size: 13.5px; margin-left: auto; }

.q { padding: 14px 16px; }
.q-head { display: flex; justify-content: space-between; gap: 8px; align-items: flex-start; }
.q-num { font-size: 12.5px; color: var(--muted); }
.q-text { margin: 4px 0 10px; font-weight: 600; white-space: pre-wrap; }
.q-code { border: 1px solid var(--line); border-radius: 8px; margin: 0 0 10px; }
.badge { font-size: 12px; padding: 2px 8px; border-radius: 99px; background: var(--brand-soft); color: var(--brand); white-space: nowrap; }
.badge.ok { background: var(--ok-soft); color: var(--ok); }
.badge.bad { background: var(--bad-soft); color: var(--bad); }
textarea { width: 100%; min-height: 96px; padding: 10px; resize: vertical; line-height: 1.55; }
.q-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.answer { margin-top: 12px; border-top: 1px dashed var(--line); padding-top: 12px; }
.answer h5 { margin: 0 0 6px; font-size: 13.5px; color: var(--muted); }
.model { background: var(--brand-soft); border-radius: 8px; padding: 10px 12px; white-space: pre-wrap; font-size: 14.5px; }
.checks { list-style: none; padding: 0; margin: 6px 0 0; }
.checks label { display: flex; gap: 8px; align-items: flex-start; cursor: pointer; padding: 4px 0; font-size: 14.5px; }
.checks input { margin-top: 5px; accent-color: var(--brand); }
.empty { text-align: center; color: var(--muted); padding: 40px 0; }

.cheat { margin-bottom: 14px; }

/* 핵심 정리 */
.final-note { margin: 0 0 10px; color: var(--muted); font-size: 14px; }
.final { padding: 12px 16px 4px; }
.final-h { margin: 0 0 4px; }
.fq { padding: 10px 0; border-top: 1px solid var(--line); }
.final-h + .fq { border-top: 0; padding-top: 4px; }
.fq-h { display: flex; gap: 8px; align-items: baseline; }
.fq-h .q-num { flex: none; font-weight: 700; color: var(--brand); }
.fq-q { flex: 1; font-weight: 600; font-size: 14.5px; }
.fq ul { margin: 6px 0 0; padding-left: 20px; font-size: 14.5px; }
.fq li { margin: 3px 0; }
.foot { max-width: 880px; margin: 0 auto; padding: 0 16px 40px; color: var(--muted); font-size: 12.5px; }

/* 주제 바로가기 */
.topic-nav {
  position: sticky; top: var(--top-h, 96px); z-index: 9;
  display: flex; gap: 6px; overflow-x: auto; scrollbar-width: none;
  margin: -8px -16px 6px; padding: 8px 16px; background: var(--bg);
}
.topic-nav::-webkit-scrollbar { display: none; }
.topic-nav button {
  flex: none; border: 1px solid var(--line); background: var(--card); color: var(--ink);
  border-radius: 99px; padding: 6px 12px; font: inherit; font-size: 13.5px; cursor: pointer; white-space: nowrap;
}
.topic-nav .n { color: var(--brand); font-weight: 700; margin-right: 5px; }
.topic-nav button.on { background: var(--brand); color: var(--brand-ink); border-color: var(--brand); }
.topic-nav button.on .n { color: inherit; }
#notes-list details { scroll-margin-top: calc(var(--top-h, 96px) + 56px); }
.search { flex: 1; min-width: 180px; cursor: text; }

/* 서술형: 카드/목록 전환, 카드 넘기기 */
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; flex: none; }
.seg button { border: 0; background: var(--card); color: var(--muted); padding: 7px 14px; font: inherit; font-size: 14px; font-weight: 600; cursor: pointer; }
.seg button + button { border-left: 1px solid var(--line); }
.seg button[aria-pressed="true"] { background: var(--brand); color: var(--brand-ink); }
#q-topic { flex: 1; }
.qprog { height: 4px; background: var(--line); border-radius: 99px; overflow: hidden; margin: 0 0 10px; }
.qprog i { display: block; height: 100%; background: var(--brand); transition: width 0.2s; }
.qnav { display: flex; align-items: center; gap: 10px; margin: 0 0 14px; }
.qnav .btn { flex: 1; min-height: 46px; font-size: 15px; }
.qnav .btn:disabled { opacity: 0.4; cursor: default; }
.qnav .pos { min-width: 64px; text-align: center; color: var(--muted); font-size: 14px; font-variant-numeric: tabular-nums; }
.draft > summary { list-style: none; cursor: pointer; color: var(--brand); font-size: 14px; font-weight: 600; padding: 4px 0; }
.draft > summary::-webkit-details-marker { display: none; }
.draft > summary::before { content: "▸ "; }
.draft[open] > summary::before { content: "▾ "; }
.draft textarea { margin-top: 6px; }
.q-actions.grade .btn { flex: 1; }

/* PDF · 앱 안내 */
.downloads p { color: var(--muted); font-size: 14px; margin: 10px 0 0; }
.dl-row { display: flex; flex-wrap: wrap; gap: 8px; }
.dl-row .btn { text-decoration: none; display: inline-flex; align-items: center; }

/* 폰 화면 */
@media screen and (max-width: 640px) {
  body { padding-bottom: calc(64px + env(safe-area-inset-bottom)); -webkit-tap-highlight-color: transparent; }
  .top { backdrop-filter: none; background: var(--bg); }
  .top-inner {
    padding: calc(8px + env(safe-area-inset-top)) max(12px, env(safe-area-inset-right)) 8px max(12px, env(safe-area-inset-left));
  }
  h1 { font-size: 17px; }
  .tools a, .tools button { padding: 7px 11px; font-size: 14px; }

  .tabs {
    position: fixed; left: 0; right: 0; bottom: 0; z-index: 30; margin: 0; gap: 0; overflow: visible;
    background: var(--card); border-top: 1px solid var(--line); box-shadow: 0 -4px 16px rgb(0 0 0 / 6%);
    padding: 0 env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);
  }
  .tab {
    flex: 1; flex-direction: column; justify-content: center; gap: 2px; padding: 7px 0 6px; min-height: 58px;
    font-size: 11.5px; border-bottom: 0; border-top: 2.5px solid transparent;
  }
  .tab svg { width: 22px; height: 22px; }
  .tab[aria-selected="true"] { border-top-color: var(--brand); }

  main { padding: 12px max(12px, env(safe-area-inset-right)) 16px max(12px, env(safe-area-inset-left)); }
  .topic-nav { margin: -4px -12px 4px; padding: 8px 12px; }
  .card > summary { padding: 12px 14px; }
  .card h3 { font-size: 16px; }
  .card-body { padding: 2px 12px 14px; }
  .q { padding: 14px; }
  h4 { margin-top: 18px; }

  /* 16px 미만 입력창은 iOS가 포커스 때 화면을 확대함 */
  input, input.chip, select, textarea { font-size: 16px; }
  .chip, .btn, select { min-height: 40px; }
  .bar { gap: 6px; }
  .stats { margin-left: 0; width: 100%; }
  .lg { display: none; }
  .search { min-width: 0; }

  pre { white-space: pre-wrap; overflow-wrap: anywhere; font-size: 12.5px; }
  table { font-size: 14px; }
  th, td { padding: 7px 8px; }
  .notes { font-size: 14px; }
  .foot { padding: 0 12px 24px; }
}