/* 영문법의 핵 — 표지에서 온 정체성: 종이색 바탕, 굵은 검정 한글, 코발트 궤도
   레이아웃: 한 줄 읽기(본문 약 680px), 첫 화면만 넓게(차례 행 + 궤도 그림) */
:root {
  --paper: #f3f0ea;
  --card: #fbfaf7;
  --ink: #15161a;
  --mute: #63646b;
  --line: #dcd7cc;
  --cobalt: #1f47c9;
  --cobalt-soft: #e2e7f7;
  --ok: #18794e;
  --ok-soft: #dff1e7;
  --ng: #c2362f;
  --ng-soft: #f8e1df;
  --f-ko: "Noto Sans KR", "Apple SD Gothic Neo", "Malgun Gothic", system-ui, sans-serif;
  --f-en: "Source Serif 4", Georgia, "Times New Roman", serif;
  --r: 10px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #121318; --card: #1a1c22; --ink: #ecebe6; --mute: #a2a3ab; --line: #2d3039;
    --cobalt: #8aa4ff; --cobalt-soft: #1d2747; --ok: #63d49c; --ok-soft: #14301f; --ng: #ff8a80; --ng-soft: #3a1c1b;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #121318; --card: #1a1c22; --ink: #ecebe6; --mute: #a2a3ab; --line: #2d3039;
  --cobalt: #8aa4ff; --cobalt-soft: #1d2747; --ok: #63d49c; --ok-soft: #14301f; --ng: #ff8a80; --ng-soft: #3a1c1b;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 72px; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--f-ko); font-size: 17px; line-height: 1.78; word-break: keep-all; overflow-wrap: break-word; }
a { color: var(--cobalt); text-underline-offset: 3px; }
:focus-visible { outline: 2px solid var(--cobalt); outline-offset: 2px; border-radius: 4px; }
[lang="en"] { word-break: normal; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.muted { color: var(--mute); }

/* 위 막대 */
body::before { content: ""; position: fixed; inset: 0 0 auto; height: env(safe-area-inset-top, 0px); z-index: 10; background: var(--paper); }
.bar { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 5; background: var(--paper); border-bottom: 1px solid var(--line); }
.bar-in, .wrap, .foot-in { max-width: 760px; margin: 0 auto; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); }
.bar-in { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 4px 18px; padding-block: 10px; }
.logo { display: inline-flex; align-items: center; gap: 9px; font-weight: 900; font-size: 19px; letter-spacing: -.02em; color: var(--ink); text-decoration: none; }
.nuc { width: 18px; height: 18px; border-radius: 50%; border: 1.5px solid var(--cobalt); position: relative; flex: none; }
.nuc::after { content: ""; position: absolute; inset: 4px; border-radius: 50%; background: var(--cobalt); }
.nav { display: flex; flex-wrap: wrap; gap: 0 16px; font-size: 15px; }
.nav a { color: var(--mute); text-decoration: none; padding: 4px 0; border-bottom: 2px solid transparent; }
.nav a:hover { color: var(--ink); }
.nav a[aria-current="page"] { color: var(--ink); font-weight: 700; border-bottom-color: var(--cobalt); }
.nav .nav-book { color: var(--cobalt); font-weight: 700; }

.wrap { padding-block: 22px 56px; }
.crumbs { font-size: 13px; color: var(--mute); margin: 0 0 14px; }
.crumbs a { color: var(--mute); }
.crumbs .sep { margin: 0 7px; opacity: .6; }
.lede { color: var(--mute); }

/* 버튼 */
.btn { display: inline-flex; align-items: center; justify-content: center; font: inherit; font-size: 15px; font-weight: 700; padding: 9px 20px; border-radius: 99px; border: 1.5px solid var(--cobalt); background: var(--cobalt); color: var(--paper); text-decoration: none; cursor: pointer; }
.btn.ghost { background: transparent; color: var(--cobalt); }

/* ---------- 첫 화면 ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 1fr) 220px; gap: 12px 28px; align-items: center; padding: 18px 0 26px; border-bottom: 1px solid var(--line); }
.kicker { margin: 0; font-size: 12px; font-weight: 700; letter-spacing: .26em; color: var(--mute); }
.hero h1 { font-size: clamp(44px, 11vw, 68px); font-weight: 900; line-height: 1.08; letter-spacing: -.04em; margin: 6px 0 6px; }
.hero-sub { margin: 0 0 14px; font-size: clamp(19px, 4.6vw, 23px); font-weight: 700; color: var(--cobalt); }
.hero-lead { margin: 0 0 18px; color: var(--mute); max-width: 34em; }
.stats { display: flex; gap: 26px; margin: 0 0 20px; }
.stats div { display: flex; flex-direction: column-reverse; }
.stats dt { font-size: 13px; color: var(--mute); }
.stats dd { margin: 0; font-size: 30px; font-weight: 900; line-height: 1.1; font-variant-numeric: tabular-nums; }
.hero-btns { display: flex; flex-wrap: wrap; gap: 8px; }
.orbit { width: 100%; max-width: 220px; height: auto; justify-self: center; }
.o-ring { fill: none; stroke: var(--cobalt); stroke-width: 1.3; opacity: .85; }
.o-dot { fill: var(--cobalt); }
.o-nuc { fill: var(--cobalt); }
@media (prefers-reduced-motion: no-preference) {
  .orbit { animation: spin 90s linear infinite; }
  @keyframes spin { to { transform: rotate(360deg); } }
}
@media (max-width: 600px) {
  .hero { grid-template-columns: 1fr; }
  .orbit { order: -1; max-width: 120px; justify-self: start; }
}

.how { padding: 18px 0 6px; }
.steps { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: 10px; counter-reset: s; }
.steps li { counter-increment: s; font-size: 14.5px; color: var(--mute); padding: 12px 14px; border: 1px solid var(--line); border-radius: var(--r); background: var(--card); }
.steps b { display: block; color: var(--ink); font-size: 15.5px; }
.steps b::before { content: counter(s) ". "; color: var(--cobalt); }

.part { margin-top: 38px; }
.part-h { display: grid; grid-template-columns: 40px minmax(0, 1fr); column-gap: 12px; align-items: center; margin-bottom: 6px; }
.part-h h2 { margin: 0; font-size: 24px; font-weight: 900; letter-spacing: -.02em; line-height: 1.3; }
.part-h h2 small { display: block; font-size: 12px; font-weight: 700; letter-spacing: .14em; color: var(--cobalt); text-transform: uppercase; }
.part-meta { grid-column: 2; margin: 0; font-size: 13.5px; color: var(--mute); }
.part-ring { grid-row: span 2; width: 40px; height: 40px; border-radius: 50%; border: 1.5px solid var(--cobalt); position: relative; }
.part-ring::after { content: ""; position: absolute; inset: 15px; border-radius: 50%; background: var(--cobalt); }
.part-ring[data-p="2"] { box-shadow: inset 0 0 0 5px var(--paper), inset 0 0 0 6.5px var(--cobalt); }
.part-ring[data-p="3"] { box-shadow: inset 0 0 0 4px var(--paper), inset 0 0 0 5.5px var(--cobalt), inset 0 0 0 9px var(--paper), inset 0 0 0 10.5px var(--cobalt); }
.part-ring[data-p="4"] { box-shadow: inset 0 0 0 3px var(--paper), inset 0 0 0 4.5px var(--cobalt), inset 0 0 0 7px var(--paper), inset 0 0 0 8.5px var(--cobalt), inset 0 0 0 11px var(--paper), inset 0 0 0 12.5px var(--cobalt); }
.part-ring[data-p="4"]::after { inset: 16px; }

.rows { list-style: none; margin: 0; padding: 0; border-top: 1.5px solid var(--ink); }
.row { display: grid; grid-template-columns: 38px minmax(0, 1fr) auto; gap: 4px 12px; padding: 14px 0; border-bottom: 1px solid var(--line); }
.row-no { font-weight: 900; color: var(--cobalt); font-variant-numeric: tabular-nums; padding-top: 1px; }
.row-t { color: var(--ink); text-decoration: none; font-weight: 700; font-size: 17.5px; }
.row-t:hover { color: var(--cobalt); }
.row-en { display: block; font-family: var(--f-en); font-weight: 400; font-size: 13px; letter-spacing: .06em; color: var(--mute); }
.row-sum { margin: 4px 0 0; font-size: 14.5px; color: var(--mute); line-height: 1.65; }
.row-side { display: flex; flex-direction: column; align-items: flex-end; gap: 6px; padding-top: 2px; }
.row-ex { font-size: 13.5px; font-weight: 700; white-space: nowrap; text-decoration: none; padding: 4px 11px; border: 1px solid var(--cobalt); border-radius: 99px; }
.row-ex:hover { background: var(--cobalt); color: var(--paper); }
.row-ex.none { border-color: var(--line); color: var(--mute); font-weight: 400; }
@media (max-width: 520px) {
  .row { grid-template-columns: 30px minmax(0, 1fr); }
  .row-side { grid-column: 2; flex-direction: row; align-items: center; justify-content: flex-start; flex-wrap: wrap; }
}
[data-ch].has { display: inline-flex; align-items: center; gap: 7px; font-size: 12.5px; color: var(--mute); font-variant-numeric: tabular-nums; }
.pbar { width: 54px; height: 5px; border-radius: 9px; background: var(--line); overflow: hidden; }
.pbar i { display: block; height: 100%; background: var(--ok); }

.play { margin-top: 44px; }
.play h2, .bookbox h2 { font-size: 22px; font-weight: 900; margin: 0 0 12px; }
.play-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 12px; }
.play-card { display: flex; flex-direction: column; gap: 4px; padding: 16px 18px; border-radius: var(--r); border: 1px solid var(--line); background: var(--card); color: var(--ink); text-decoration: none; }
.play-card b { font-size: 18px; color: var(--cobalt); }
.play-card span { font-size: 14.5px; color: var(--mute); }
.play-card:hover { border-color: var(--cobalt); }
.bookbox { margin-top: 44px; display: grid; grid-template-columns: 120px minmax(0, 1fr); gap: 20px; align-items: center; padding-top: 28px; border-top: 1.5px solid var(--ink); }
.bookbox img { width: 120px; height: auto; border-radius: 3px; box-shadow: 0 6px 18px rgba(0, 0, 0, .18); }
.bookbox p { margin: 0 0 12px; color: var(--mute); }

/* ---------- 장 머리 ---------- */
.ch-head { margin: 0 0 26px; }
.ch-part { margin: 0 0 4px; font-size: 13px; font-weight: 700; letter-spacing: .06em; color: var(--cobalt); }
.ch-head h1 { margin: 0; font-size: clamp(28px, 7vw, 38px); font-weight: 900; line-height: 1.25; letter-spacing: -.03em; display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.ch-no { color: var(--cobalt); font-variant-numeric: tabular-nums; }
.ch-en { margin: 4px 0 0; font-family: var(--f-en); font-size: 14px; letter-spacing: .14em; color: var(--mute); }

/* ---------- 책 본문 ---------- */
.book .block { padding: 0 0 6px; margin: 0 0 26px; }
.book h2 { font-size: 13px; font-weight: 700; letter-spacing: .12em; color: var(--cobalt); margin: 0 0 10px; display: flex; align-items: center; gap: 10px; }
.book h2::after { content: ""; flex: 1; height: 1px; background: var(--line); }
.book .block:not(.block-def):not(.block-ex):not(.block-note):not(.block-sum) > h2 { font-size: 19px; letter-spacing: 0; color: var(--ink); }
.book p { margin: 0 0 .9em; }
.book .def-item { font-size: 18.5px; line-height: 1.7; }
.book .term { color: var(--cobalt); }
.book b.w, .book [lang="en"] b { font-weight: 600; }
.book [lang="en"] { font-family: var(--f-en); font-size: 1.04em; }
.book b.w[lang="en"] { font-family: var(--f-en); }
.book .examples { margin: 0; padding: 14px 18px 14px 42px; background: var(--card); border: 1px solid var(--line); border-radius: var(--r); }
.book .examples li { padding: 2px 0; }
.book .examples li::marker { color: var(--cobalt); font-family: var(--f-ko); font-size: .85em; font-weight: 700; }
.book .explain { margin: 0; padding-left: 1.2em; }
.book .explain li { margin-bottom: .5em; }
.book .explain li::marker { color: var(--cobalt); }
.book .table-wrap { overflow-x: auto; margin: 6px 0 14px; border: 1px solid var(--line); border-radius: var(--r); background: var(--card); }
.book table { border-collapse: collapse; width: 100%; font-size: 15px; }
.book caption { text-align: left; font-weight: 700; padding: 10px 14px 0; }
.book th, .book td { text-align: left; padding: 8px 14px; border-bottom: 1px solid var(--line); vertical-align: top; }
.book tr:last-child td { border-bottom: 0; }
.book th { font-size: 13px; color: var(--mute); font-weight: 700; }
.book .rowhead { font-weight: 600; white-space: nowrap; }
.book .tip { margin: 14px 0 6px; padding: 12px 16px; border-left: 3px solid var(--cobalt); background: var(--cobalt-soft); border-radius: 0 var(--r) var(--r) 0; }
.book .tip p:last-child { margin-bottom: 0; }
.book .tip-label { display: block; font-size: 13px; color: var(--cobalt); margin-bottom: 2px; }
.book .ex-pair { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 10px; margin: 0 0 1em; padding: 10px 14px; background: var(--card); border: 1px solid var(--line); border-radius: var(--r); }
.book .ex-label { font-weight: 700; color: var(--cobalt); }
.book .block-sum { padding: 16px 18px 8px; border: 1.5px solid var(--ink); border-radius: var(--r); }
.book .block-sum p { font-size: 17.5px; font-weight: 500; }
.book ul:not(.explain), .book ol:not(.examples) { padding-left: 1.3em; }

.cta { margin: 32px 0 8px; padding: 20px 20px 18px; border-radius: var(--r); background: var(--cobalt); color: var(--paper); }
.cta-k { margin: 0 0 6px; font-weight: 900; font-size: 19px; }
.cta-sets { margin: 0 0 14px; padding-left: 1.2em; font-size: 14.5px; opacity: .92; }
.cta .btn { background: var(--paper); color: var(--cobalt); border-color: var(--paper); }
.cta [data-ch].has { color: var(--paper); margin-left: 12px; }
.cta .pbar { background: rgba(255, 255, 255, .3); }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 40px; padding-top: 16px; border-top: 1px solid var(--line); }
.pager a { display: flex; flex-direction: column; font-size: 15px; text-decoration: none; color: var(--ink); font-weight: 700; min-width: 0; }
.pager small { font-size: 12px; font-weight: 400; color: var(--mute); }
.pager .next { text-align: right; align-items: flex-end; }

/* ---------- 연습문제 ---------- */
.links3 { display: flex; flex-direction: column; gap: 2px; margin: -8px 0 22px; padding: 12px 16px; border-radius: var(--r); background: var(--card); border: 1px solid var(--line); font-size: 15px; }
.ex-top { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 4px 18px; position: sticky; top: calc(env(safe-area-inset-top, 0px) + 49px); z-index: 3; background: var(--paper); padding: 8px 0; border-bottom: 1px solid var(--line); }
.ex-how { margin: 0; font-size: 13.5px; color: var(--mute); flex: 1 1 260px; min-width: 0; }
.ex-score { margin: 0; font-size: 14px; font-variant-numeric: tabular-nums; }
.ex-score b { font-size: 20px; color: var(--ok); }
.ex-prev { font-size: 13.5px; color: var(--mute); margin: 10px 0 0; }
.set { margin-top: 26px; }
.set-h { font-size: 17px; font-weight: 700; line-height: 1.55; margin: 0 0 4px; }
.items { list-style: none; margin: 0; padding: 0; }
.item { display: grid; grid-template-columns: 28px minmax(0, 1fr); gap: 10px; padding: 14px 0; border-bottom: 1px solid var(--line); }
.item-no { font-size: 13px; font-weight: 700; color: var(--mute); padding-top: 6px; font-variant-numeric: tabular-nums; }
.item-b { min-width: 0; }
.q-en, .toks { margin: 0 0 8px; font-family: var(--f-en); font-size: 19px; line-height: 1.9; }
.tok { font: inherit; color: inherit; background: transparent; border: 0; border-bottom: 2px dotted var(--line); padding: 0 2px; margin: 0 1px; border-radius: 3px; cursor: pointer; }
.tok:hover { background: var(--cobalt-soft); }
.tok[aria-pressed="true"] { background: var(--cobalt); color: var(--paper); border-bottom-color: var(--cobalt); }
.tok.none { font-family: var(--f-ko); font-size: 14px; border: 1px solid var(--line); padding: 4px 12px; border-radius: 99px; }
.tok.hit { background: var(--ok-soft); color: var(--ok); border-bottom: 2px solid var(--ok); }
.tok.miss { background: var(--ng-soft); color: var(--ng); text-decoration: line-through; border-bottom-color: var(--ng); }
.tok:disabled { cursor: default; }
.acts, .ops { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; }
.ops { margin: 4px 0 8px; }
.ops-k { font-size: 12.5px; color: var(--mute); width: 100%; }
.op, .chk { font: inherit; font-size: 15px; padding: 6px 14px; border-radius: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink); cursor: pointer; }
.op:hover:not(:disabled) { border-color: var(--cobalt); }
.op[aria-pressed="true"] { border-color: var(--cobalt); background: var(--cobalt-soft); }
.op:disabled { cursor: default; opacity: .55; }
.op.hit { opacity: 1; border-color: var(--ok); background: var(--ok-soft); color: var(--ok); font-weight: 700; }
.op.miss { opacity: 1; border-color: var(--ng); background: var(--ng-soft); color: var(--ng); text-decoration: line-through; }
.chk { background: var(--cobalt); border-color: var(--cobalt); color: var(--paper); font-weight: 700; }
.slot { display: inline-block; min-width: 3em; border-bottom: 2px solid var(--ink); text-align: center; line-height: 1.3; }
.slot.filled { color: var(--cobalt); border-color: var(--cobalt); font-weight: 600; }
.slot.hit { color: var(--ok); border-color: var(--ok); }
.slot.miss { color: var(--ng); border-color: var(--ng); }
.w-in { display: block; width: 100%; font-family: var(--f-en); font-size: 17px; line-height: 1.6; padding: 8px 12px; margin: 0 0 8px; border: 1px solid var(--line); border-radius: 8px; background: var(--card); color: var(--ink); resize: none; }
.w-in:focus { border-color: var(--cobalt); outline: none; }
.step { margin-top: 6px; }
.step-q { margin: 0; font-size: 15px; }
.step-q b { font-family: var(--f-en); color: var(--cobalt); }
.self, .fb { margin-top: 8px; padding: 10px 14px; border-radius: 8px; background: var(--card); border: 1px solid var(--line); font-size: 15px; }
.self p, .fb p { margin: 0; }
.self-q { color: var(--mute); margin-top: 4px !important; font-size: 14px; }
.fb-v { font-weight: 700; }
.ok > .fb .fb-v { color: var(--ok); }
.ng > .fb .fb-v { color: var(--ng); }
.fb-k { display: inline-block; font-size: 12px; font-weight: 700; color: var(--paper); background: var(--mute); border-radius: 4px; padding: 0 6px; margin-right: 4px; vertical-align: 1px; }
.fb-a [lang="en"], .fb-a b.w { font-family: var(--f-en); }
.fb-x { color: var(--mute); margin-top: 4px !important; }
.result { margin-top: 26px; padding: 22px; border-radius: var(--r); border: 1.5px solid var(--ink); text-align: center; }
.result p { margin: 0 0 12px; }
.result-n { font-size: 38px; font-weight: 900; color: var(--cobalt); font-variant-numeric: tabular-nums; }
.result-btns { display: flex; flex-wrap: wrap; justify-content: center; gap: 8px; }

/* 연습문제 모음 */
.excs { list-style: none; margin: 0; padding: 0; border-top: 1.5px solid var(--ink); }
.exc { padding: 14px 0; border-bottom: 1px solid var(--line); }
.exc-h { display: flex; align-items: baseline; gap: 10px; font-weight: 700; font-size: 17.5px; color: var(--ink); text-decoration: none; }
.exc-h:hover { color: var(--cobalt); }
.exc-h .row-no { width: 28px; flex: none; }
.exc-n { margin-left: auto; font-size: 13.5px; color: var(--cobalt); white-space: nowrap; }
.exc-sets { margin: 4px 0 0 38px; padding-left: 1.1em; font-size: 14px; color: var(--mute); }
.exc [data-ch].has { margin: 6px 0 0 38px; }

/* 용어 사전 */
.gl-search input { width: 100%; font: inherit; padding: 10px 14px; border: 1px solid var(--line); border-radius: 99px; background: var(--card); color: var(--ink); }
.gl-search input:focus { border-color: var(--cobalt); outline: none; }
.gl-nav { display: flex; flex-wrap: wrap; gap: 4px; margin: 14px 0 6px; position: sticky; top: calc(env(safe-area-inset-top, 0px) + 49px); background: var(--paper); padding: 6px 0; z-index: 2; }
.gl-nav a { min-width: 34px; text-align: center; padding: 3px 8px; border-radius: 6px; border: 1px solid var(--line); text-decoration: none; font-weight: 700; font-size: 14px; }
.glossary .index-letter { font-size: 22px; font-weight: 900; color: var(--cobalt); margin: 22px 0 4px; }
.glossary .index-list { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--ink); }
.glossary .index-list li { display: flex; flex-wrap: wrap; align-items: baseline; gap: 2px 10px; padding: 8px 0; border-bottom: 1px solid var(--line); }
.glossary .index-term { font-weight: 700; }
.glossary .index-en { font-family: var(--f-en); color: var(--mute); font-size: 15px; }
.glossary .index-refs { margin-left: auto; display: flex; gap: 6px; }
.glossary .index-refs a { font-size: 13.5px; font-weight: 700; text-decoration: none; padding: 1px 9px; border-radius: 99px; background: var(--cobalt-soft); }

.foot { border-top: 1px solid var(--line); }
.foot-in { padding-block: 22px 30px; font-size: 14px; color: var(--mute); }
.foot p { margin: 0 0 4px; }
.foot .small { font-size: 12.5px; }
.logo-s { font-size: 12px; font-weight: 700; color: var(--cobalt); letter-spacing: .02em; margin-left: 2px; }
.result-book { margin: 14px 0 0 !important; font-size: 14px; color: var(--mute); }