/* ============================================================
   사내 AI 강의 시리즈 — 공통 스타일 (6강 표준 템플릿)
   - 외부 폰트/CDN 의존성 없음 (사내 보안 환경 고려, 오프라인 동작)
   - 색/타이포/레이아웃을 CSS 변수로 토큰화하여 6강 재사용
   ============================================================ */

:root {
  --ink:        #20241f;   /* 본문 잉크 */
  --ink-soft:   #4a4f47;
  --muted:      #797d72;
  --paper:      #faf7f0;   /* 종이/책상 느낌의 따뜻한 바탕 */
  --paper-2:    #f2ede2;
  --line:       #e4ddcd;
  --accent:     #0f766e;   /* HOW — 차분한 teal */
  --accent-amber:#b9700d;  /* WHY / "책상 위" 메타포 강조 */
  --accent-deep:#1f513f;   /* WHAT */
  --note-bg:    #1c211c;   /* 강사 노트 = 무대 뒤(backstage) 다크 패널 */
  --note-ink:   #e8e4d8;
  --note-accent:#7fd1c4;
  --maxw:       760px;
  --font: "Pretendard", -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo",
          "Malgun Gothic", "맑은 고딕", "Segoe UI", system-ui, sans-serif;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ---------- 상단 진행 바 + 강의 타이틀 ---------- */
.topbar {
  position: fixed; top: 0; left: 0; right: 0;
  display: flex; align-items: center; gap: 14px;
  padding: 12px 22px;
  background: rgba(250,247,240,0.88);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
  z-index: 50;
  font-size: 13px;
}
.topbar .series {
  color: var(--muted); font-weight: 600; letter-spacing: .02em;
}
.topbar .series a { color: var(--muted); text-decoration: none; }
.topbar .series a:hover { color: var(--accent); }
.topbar .lec-title {
  font-weight: 700; color: var(--ink);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.topbar .spacer { flex: 1; }
.topbar .counter { color: var(--muted); font-variant-numeric: tabular-nums; }
#progress-track {
  position: fixed; top: 0; left: 0; right: 0; height: 3px;
  background: transparent; z-index: 51;
}
#progress-bar {
  height: 100%; width: 0;
  background: linear-gradient(90deg, var(--accent-amber), var(--accent));
  transition: width .35s ease;
}

/* 강사 노트 토글 버튼 */
.notes-btn {
  border: 1px solid var(--line); background: #fff; color: var(--ink-soft);
  font: inherit; font-size: 12px; font-weight: 600;
  padding: 5px 11px; border-radius: 999px; cursor: pointer;
  transition: all .15s ease;
}
.notes-btn:hover { border-color: var(--accent); color: var(--accent); }
.notes-btn[aria-pressed="true"] {
  background: var(--note-bg); color: var(--note-accent); border-color: var(--note-bg);
}

/* ---------- 페이지(슬라이드) ---------- */
.deck { padding-top: 52px; }
.page { display: none; min-height: calc(100vh - 52px); }
.page.active {
  display: flex; flex-direction: column; justify-content: center;
  animation: fade .4s ease;
}
@keyframes fade { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

.page-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 56px 28px 40px;
  width: 100%;
}

.kicker {
  display: inline-block;
  font-size: 12px; font-weight: 800; letter-spacing: .14em;
  text-transform: uppercase;
  padding: 4px 10px; border-radius: 6px;
  margin-bottom: 22px;
}
.kicker.why  { color: var(--accent-amber); background: #f7ecda; }
.kicker.how  { color: var(--accent);       background: #d9efec; }
.kicker.what { color: var(--accent-deep);  background: #dcefe4; }
.kicker.recap{ color: var(--muted);        background: var(--paper-2); }

/* 섹션 코너 배지 (Why/How/What) — data-stage 가 있는 페이지에만, 활성 페이지만 표시.
   머리말은 제거하되 골든서클 단계만 화면 구석에 작게 남기는 용도. JS 불필요. */
.page[data-stage]::before {
  content: attr(data-stage);
  position: fixed;
  top: 60px; left: 20px;
  font-size: 11px; font-weight: 800; letter-spacing: .16em;
  padding: 5px 10px; border-radius: 7px;
  background: #fff; border: 1px solid var(--line);
  color: var(--muted);
  z-index: 40; pointer-events: none;
}
.page[data-stage="WHY"]::before  { color: var(--accent-amber); background: #faf2e3; border-color: #ecdcc0; }
.page[data-stage="HOW"]::before  { color: var(--accent);       background: #dcefe9; border-color: #bfe3dd; }
.page[data-stage="WHAT"]::before { color: var(--accent-deep);  background: #dcefe4; border-color: #cfe6d9; }
@media (max-width: 720px) {
  .page[data-stage]::before { top: auto; bottom: 66px; left: 14px; font-size: 10px; padding: 4px 8px; }
}

h1 {
  font-size: clamp(28px, 4.4vw, 44px);
  line-height: 1.22; font-weight: 800; letter-spacing: -.01em;
  margin: 0 0 18px;
}
h2 {
  font-size: clamp(22px, 3vw, 30px);
  line-height: 1.3; font-weight: 800; margin: 0 0 16px;
}
.lead {
  font-size: clamp(18px, 2.2vw, 22px);
  color: var(--ink-soft); font-weight: 500;
  margin: 0 0 18px;
}
p { margin: 0 0 16px; font-size: 17px; }
strong { color: var(--ink); font-weight: 800; }
em { font-style: normal; color: var(--accent-amber); font-weight: 700; }

/* 큰 결론 한 줄 */
.punch {
  font-size: clamp(24px, 3.4vw, 34px);
  font-weight: 800; line-height: 1.3; letter-spacing: -.01em;
  margin: 8px 0 22px;
}
.punch .hl { color: var(--accent); }
.punch .hl-amber { color: var(--accent-amber); }

/* 인용/원리 박스 */
.principle {
  border-left: 4px solid var(--accent-amber);
  background: #faf2e3;
  padding: 16px 20px; border-radius: 0 10px 10px 0;
  margin: 22px 0; font-size: 17px;
}
.principle .src { display:block; color: var(--muted); font-size: 13px; margin-top: 8px; font-weight:600; }

/* 카드/그리드 */
.cards { display: grid; gap: 14px; margin: 22px 0; }
.cards.two { grid-template-columns: 1fr 1fr; }
@media (max-width: 640px) { .cards.two { grid-template-columns: 1fr; } }
.card {
  background: #fff; border: 1px solid var(--line);
  border-radius: 12px; padding: 18px 20px;
}
.card h3 { margin: 0 0 8px; font-size: 16px; font-weight: 800; }
.card p  { margin: 0; font-size: 15px; color: var(--ink-soft); }
.card .tag { font-size: 12px; font-weight: 800; color: var(--accent); letter-spacing:.05em; }

/* 책상 도식 */
.desk {
  margin: 24px 0; padding: 22px; border-radius: 14px;
  background: linear-gradient(180deg, #fff, var(--paper-2));
  border: 1px solid var(--line);
}
.desk .desk-label { font-size: 12px; font-weight: 800; letter-spacing:.12em; color: var(--muted); text-transform: uppercase; margin-bottom: 12px; }
.desk .slots { display: flex; flex-wrap: wrap; gap: 10px; }
.slot {
  flex: 1 1 auto; min-width: 120px;
  background: #fff; border: 1px dashed #c9bfa6; border-radius: 8px;
  padding: 12px 14px; font-size: 14px;
}
.slot b { display:block; color: var(--accent); font-size: 12px; letter-spacing:.04em; margin-bottom: 3px; }
.slot.fade { opacity: .42; }
.slot.q { border-style: solid; border-color: var(--accent-amber); background:#fdf6ea; }

/* 리스트 */
.steps { counter-reset: s; list-style: none; padding: 0; margin: 20px 0; }
.steps li {
  position: relative; padding: 4px 0 14px 44px; font-size: 16.5px;
}
.steps li::before {
  counter-increment: s; content: counter(s);
  position: absolute; left: 0; top: 2px;
  width: 30px; height: 30px; border-radius: 50%;
  background: var(--accent); color: #fff;
  font-size: 14px; font-weight: 800;
  display: grid; place-items: center;
}
ul.ticks { list-style: none; padding: 0; margin: 18px 0; }
ul.ticks li { position: relative; padding: 4px 0 10px 30px; font-size: 16.5px; }
ul.ticks li::before { content: "→"; position: absolute; left: 0; color: var(--accent); font-weight: 800; }

/* 교차참조 칩 */
.xref {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 13px; font-weight: 700;
  padding: 4px 11px; border-radius: 999px;
  background: var(--paper-2); color: var(--ink-soft);
  border: 1px solid var(--line); margin: 4px 6px 4px 0;
}
.xref b { color: var(--accent-deep); }

/* ---------- 강사 노트 (무대 뒤) ---------- */
.notes { display: none; }
body.notes-visible .page.active .notes {
  display: block;
  max-width: var(--maxw); margin: 0 auto 40px; width: 100%;
  padding: 0 28px;
}
.notes-inner {
  background: var(--note-bg); color: var(--note-ink);
  border-radius: 14px; padding: 22px 26px;
  font-size: 15px; line-height: 1.72;
}
.notes-inner h4 {
  margin: 0 0 14px; color: var(--note-accent);
  font-size: 13px; letter-spacing: .12em; text-transform: uppercase;
}
.notes-inner p { font-size: 15px; color: var(--note-ink); margin: 0 0 12px; }
.notes-inner strong { color: #fff; }
.notes-inner code {
  background: rgba(255,255,255,.1); padding: 1px 6px; border-radius: 5px;
  font-size: 13.5px;
}
.notes-inner .term { color: var(--note-accent); font-weight: 700; }
.notes-inner ul { margin: 6px 0 12px; padding-left: 20px; }
.notes-inner li { margin-bottom: 6px; }

/* ---------- 하단 내비게이션 ---------- */
.navbar {
  position: fixed; bottom: 0; left: 0; right: 0;
  display: flex; align-items: center; justify-content: space-between;
  gap: 12px; padding: 12px 22px;
  background: rgba(250,247,240,0.9); backdrop-filter: blur(8px);
  border-top: 1px solid var(--line); z-index: 50;
}
.navbar button, .navbar a.navlink {
  font: inherit; font-size: 14px; font-weight: 700;
  border: 1px solid var(--line); background: #fff; color: var(--ink);
  padding: 9px 18px; border-radius: 10px; cursor: pointer; text-decoration: none;
  transition: all .15s ease;
}
.navbar button:hover:not(:disabled), .navbar a.navlink:hover { border-color: var(--accent); color: var(--accent); }
.navbar button:disabled { opacity: .35; cursor: default; }
.navbar .nav-mid { font-size: 12px; color: var(--muted); }
.navbar .next { background: var(--accent); color: #fff; border-color: var(--accent); }
.navbar .next:hover:not(:disabled) { background: var(--accent-deep); color:#fff; }

.hint { color: var(--muted); font-size: 12px; }

/* ---------- 시리즈 인덱스 ---------- */
.index-wrap { max-width: 880px; margin: 0 auto; padding: 80px 28px 80px; }
.index-wrap .eyebrow { color: var(--accent-amber); font-weight: 800; letter-spacing:.14em; text-transform: uppercase; font-size: 13px; }
.index-wrap h1 { font-size: clamp(30px, 5vw, 50px); margin: 10px 0 16px; }
.index-wrap .sub { font-size: 18px; color: var(--ink-soft); max-width: 620px; margin-bottom: 14px;}
.spine {
  background: #faf2e3; border: 1px solid #ecdcc0; border-radius: 12px;
  padding: 16px 20px; margin: 24px 0 36px; font-size: 15px; color: var(--ink-soft);
}
.spine b { color: var(--accent-amber); }
.track-label { font-size: 13px; font-weight: 800; letter-spacing:.06em; color: var(--muted); margin: 28px 0 12px; }
.lec-list { display: grid; gap: 12px; }
.lec-item {
  display: flex; align-items: center; gap: 18px;
  background: #fff; border: 1px solid var(--line); border-radius: 14px;
  padding: 18px 22px; text-decoration: none; color: inherit;
  transition: all .15s ease;
}
.lec-item.live:hover { border-color: var(--accent); transform: translateX(3px); box-shadow: 0 6px 22px rgba(15,118,110,.10); }
.lec-item.soon { opacity: .6; cursor: default; }
.lec-num {
  flex: 0 0 auto; width: 46px; height: 46px; border-radius: 12px;
  background: var(--paper-2); color: var(--ink);
  display: grid; place-items: center; font-weight: 800; font-size: 18px;
}
.lec-item.live .lec-num { background: var(--accent); color: #fff; }
.lec-body { flex: 1; }
.lec-body h3 { margin: 0 0 3px; font-size: 17px; font-weight: 800; }
.lec-body p { margin: 0; font-size: 14px; color: var(--muted); }
.lec-status { font-size: 12px; font-weight: 800; letter-spacing:.04em; }
.lec-item.live .lec-status { color: var(--accent); }
.lec-item.soon .lec-status { color: var(--muted); }