:root {
  --bg: #faf7f2;
  --surface: #ffffff;
  --surface-2: #f3eee6;
  --line: #e7dfd3;
  --text: #2b2620;
  --muted: #8a8076;
  --accent: #f08c2e;
  --accent-soft: #fff1e2;
  --accent-ink: #b35c0c;
  --good: #2f9e6a;
  --good-soft: #e3f5ec;
  --bad: #d9534f;
  --bad-soft: #fdeaea;
  --lock: #bdb4a9;
  --shadow: 0 1px 2px rgba(60, 40, 20, .06), 0 4px 16px rgba(60, 40, 20, .06);
  --radius: 14px;
  --sidebar-w: 340px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #17140f;
    --surface: #211d17;
    --surface-2: #2a251e;
    --line: #3a332a;
    --text: #f1ebe3;
    --muted: #a39889;
    --accent: #f59b45;
    --accent-soft: #3a2a19;
    --accent-ink: #ffc68f;
    --good: #4cc08a;
    --good-soft: #1b3428;
    --bad: #f07470;
    --bad-soft: #3c1f1e;
    --lock: #5d554b;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 16px rgba(0, 0, 0, .25);
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  font-family: Pretendard, -apple-system, "Apple SD Gothic Neo", "Malgun Gothic", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}
button, input, select { font: inherit; color: inherit; }
button { cursor: pointer; }
.muted { color: var(--muted); }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 30;
  display: flex; align-items: center; gap: 16px;
  padding: 10px 20px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; min-width: 0; }
.brand-mark {
  width: 36px; height: 36px; border-radius: 10px; flex: none;
  display: grid; place-items: center;
  background: var(--accent); color: #fff; font-weight: 800; font-size: 18px;
}
.brand-title { font-weight: 800; font-size: 16px; white-space: nowrap; }
.brand-sub { font-size: 12px; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.overall { flex: 1; max-width: 360px; margin-left: auto; }
.overall-label { font-size: 12px; color: var(--muted); text-align: right; margin-bottom: 4px; }
.bar { height: 8px; border-radius: 99px; background: var(--surface-2); overflow: hidden; }
.bar-fill { height: 100%; width: 0; background: var(--accent); border-radius: 99px; transition: width .4s ease; }
.top-actions { display: flex; align-items: center; gap: 8px; }
.icon-btn {
  width: 38px; height: 38px; border-radius: 10px; border: 1px solid var(--line);
  background: var(--surface); font-size: 18px; display: grid; place-items: center;
}
.icon-btn:hover { background: var(--surface-2); }
.menu-btn { display: none; }
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 7px 12px; border-radius: 99px; border: 1px solid var(--line);
  background: var(--surface); font-size: 14px; font-weight: 600;
}
.chip:hover { background: var(--surface-2); }
.badge {
  min-width: 20px; padding: 0 6px; height: 20px; border-radius: 99px;
  background: var(--bad); color: #fff; font-size: 12px; display: inline-grid; place-items: center;
}
.badge.zero { background: var(--lock); }

/* ---------- layout ---------- */
.layout { display: flex; min-height: calc(100vh - 59px); }
.sidebar {
  width: var(--sidebar-w); flex: none;
  border-right: 1px solid var(--line);
  background: var(--surface);
  height: calc(100vh - 59px); position: sticky; top: 59px;
  overflow-y: auto;
}
.sidebar-head { padding: 16px 18px 8px; display: flex; flex-direction: column; gap: 2px; font-size: 14px; }
.sidebar-head .muted { font-size: 12px; }
.lecture-list { padding: 4px 10px 40px; }
.section-title {
  margin: 16px 8px 6px; font-size: 12px; font-weight: 700; letter-spacing: .02em;
  color: var(--accent-ink); display: flex; justify-content: space-between;
}
.section-title .muted { font-weight: 500; }
.lec-item {
  width: 100%; display: flex; align-items: flex-start; gap: 10px;
  padding: 9px 10px; border: 0; border-radius: 10px; background: transparent; text-align: left;
}
.lec-item:hover:not(:disabled) { background: var(--surface-2); }
.lec-item.active { background: var(--accent-soft); }
.lec-item:disabled { cursor: not-allowed; opacity: .55; }
.lec-status {
  width: 26px; height: 26px; flex: none; border-radius: 50%;
  display: grid; place-items: center; font-size: 12px; font-weight: 700;
  border: 2px solid var(--line); color: var(--muted); background: var(--surface);
}
.lec-status.passed { background: var(--good); border-color: var(--good); color: #fff; }
.lec-status.watched { border-color: var(--accent); color: var(--accent-ink); }
.lec-status.tried { border-color: var(--bad); color: var(--bad); }
.lec-status.locked { border-style: dashed; }
.lec-meta { min-width: 0; flex: 1; }
.lec-name { display: block; font-size: 14px; font-weight: 600; line-height: 1.35; }
.lec-sub { display: block; font-size: 12px; color: var(--muted); margin-top: 2px; }
.scrim { display: none; }

.main { flex: 1; min-width: 0; padding: 24px 32px 80px; }
.container { max-width: 880px; margin: 0 auto; }

/* ---------- lecture view ---------- */
.lec-header { margin-bottom: 14px; }
.eyebrow { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }
.tag {
  font-size: 12px; font-weight: 600; padding: 3px 9px; border-radius: 99px;
  background: var(--surface-2); color: var(--muted);
}
.tag.accent { background: var(--accent-soft); color: var(--accent-ink); }
.tag.good { background: var(--good-soft); color: var(--good); }
h1.lec-title { font-size: 24px; line-height: 1.35; margin: 0; letter-spacing: -.01em; }

.player-card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); overflow: hidden;
}
.player-wrap { position: relative; aspect-ratio: 16 / 9; background: #000; }
.player-wrap > div, .player-wrap iframe { position: absolute; inset: 0; width: 100%; height: 100%; }
.player-fallback {
  position: absolute; inset: 0; display: grid; place-items: center; color: #ddd; text-align: center; padding: 20px; font-size: 14px;
}
.watch-row { display: flex; align-items: center; gap: 14px; padding: 14px 16px; flex-wrap: wrap; }
.watch-progress { flex: 1; min-width: 200px; }
.watch-label { display: flex; justify-content: space-between; font-size: 13px; margin-bottom: 5px; }
.watch-label strong { font-weight: 700; }
.watch-row .bar-fill { background: var(--accent); }
.watch-row .bar-fill.done { background: var(--good); }
.watch-actions { display: flex; gap: 8px; flex-wrap: wrap; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  padding: 10px 16px; border-radius: 10px; border: 1px solid var(--line);
  background: var(--surface); font-weight: 600; font-size: 14px; text-decoration: none; color: var(--text);
}
.btn:hover:not(:disabled) { background: var(--surface-2); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover:not(:disabled) { filter: brightness(.95); background: var(--accent); }
.btn.ghost { background: transparent; }
.btn.danger { color: var(--bad); border-color: color-mix(in srgb, var(--bad) 40%, var(--line)); }
.btn.small { padding: 7px 12px; font-size: 13px; }
.btn.big { padding: 13px 22px; font-size: 16px; }

.card {
  margin-top: 18px; background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow); padding: 22px;
  scroll-margin-top: 76px;
}
.card h2 { margin: 0 0 6px; font-size: 18px; }
.quiz-gate { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.quiz-gate p { margin: 0; flex: 1; min-width: 220px; color: var(--muted); font-size: 14px; }
.best { font-size: 13px; color: var(--muted); margin-top: 4px; }

/* ---------- quiz ---------- */
.quiz-top { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; gap: 10px; }
.quiz-step { font-size: 13px; color: var(--muted); font-weight: 600; }
.dots { display: flex; gap: 5px; flex-wrap: wrap; }
.dot { width: 10px; height: 10px; border-radius: 50%; background: var(--surface-2); border: 1px solid var(--line); }
.dot.current { background: var(--accent); border-color: var(--accent); }
.dot.ok { background: var(--good); border-color: var(--good); }
.dot.ng { background: var(--bad); border-color: var(--bad); }
.question { font-size: 19px; font-weight: 700; line-height: 1.5; margin: 6px 0 16px; white-space: pre-wrap; }
.blank { color: var(--accent-ink); font-weight: 800; letter-spacing: .05em; }
#quizCard > .tag { display: inline-block; margin-bottom: 4px; }
.choices { display: grid; gap: 8px; }
.choice {
  display: flex; align-items: center; gap: 12px; width: 100%; text-align: left;
  padding: 13px 14px; border-radius: 12px; border: 1.5px solid var(--line); background: var(--surface);
  font-size: 16px;
}
.choice:hover:not(:disabled) { border-color: var(--accent); background: var(--accent-soft); }
.choice .key {
  width: 26px; height: 26px; flex: none; border-radius: 8px; background: var(--surface-2);
  display: grid; place-items: center; font-size: 13px; font-weight: 700; color: var(--muted);
}
.choice.selected { border-color: var(--accent); background: var(--accent-soft); }
.choice.correct { border-color: var(--good); background: var(--good-soft); }
.choice.correct .key { background: var(--good); color: #fff; }
.choice.wrong { border-color: var(--bad); background: var(--bad-soft); }
.choice.wrong .key { background: var(--bad); color: #fff; }
.choice:disabled { cursor: default; }
.answer-input {
  width: 100%; padding: 13px 14px; font-size: 17px; border-radius: 12px;
  border: 1.5px solid var(--line); background: var(--surface); outline: none;
}
.answer-input:focus { border-color: var(--accent); }
.answer-input.correct { border-color: var(--good); background: var(--good-soft); }
.answer-input.wrong { border-color: var(--bad); background: var(--bad-soft); }
.hint { font-size: 12px; color: var(--muted); margin-top: 6px; }
.feedback {
  margin-top: 14px; padding: 13px 15px; border-radius: 12px; font-size: 15px;
}
.feedback.ok { background: var(--good-soft); }
.feedback.ng { background: var(--bad-soft); }
.feedback strong { display: block; margin-bottom: 2px; }
.feedback .ok-title { color: var(--good); }
.feedback .ng-title { color: var(--bad); }
.quiz-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 16px; }

.result { text-align: center; padding: 8px 0 4px; }
.result .score { font-size: 54px; font-weight: 800; line-height: 1.1; }
.result .score small { font-size: 22px; color: var(--muted); font-weight: 700; }
.result .verdict { font-size: 18px; font-weight: 700; margin: 6px 0 4px; }
.result .verdict.pass { color: var(--good); }
.result .verdict.fail { color: var(--bad); }
.result-actions { display: flex; justify-content: center; gap: 8px; flex-wrap: wrap; margin-top: 16px; }
.review-list { margin-top: 18px; display: grid; gap: 8px; text-align: left; }
.review-item { padding: 11px 14px; border-radius: 10px; background: var(--surface-2); font-size: 14px; }
.review-item .ri-q { font-weight: 600; }
.review-item .ri-a { color: var(--good); margin-top: 2px; }
.review-item .ri-mine { color: var(--bad); }
.review-item .ri-exp { color: var(--muted); margin-top: 2px; }

.points { margin: 8px 0 0; padding-left: 20px; }
.points li { margin: 4px 0; }
.nav-row { display: flex; justify-content: space-between; gap: 8px; margin-top: 22px; }

/* ---------- wrong note ---------- */
.wn-group { margin-top: 14px; }
.wn-group h3 { font-size: 14px; margin: 0 0 6px; color: var(--accent-ink); }
.empty { text-align: center; padding: 40px 10px; color: var(--muted); }
.empty .big-emoji { font-size: 44px; }

/* ---------- dialog / toast ---------- */
.dialog {
  border: 1px solid var(--line); border-radius: 16px; padding: 0; width: min(460px, calc(100vw - 32px));
  background: var(--surface); color: var(--text); box-shadow: var(--shadow);
}
.dialog::backdrop { background: rgba(0, 0, 0, .35); }
.dialog form { padding: 22px; }
.dialog h2 { margin: 0 0 14px; font-size: 18px; }
.toggle-row { display: flex; align-items: flex-start; gap: 12px; padding: 12px 0; border-top: 1px solid var(--line); }
.toggle-row input[type=checkbox] { width: 20px; height: 20px; margin-top: 3px; accent-color: var(--accent); }
.toggle-row span { flex: 1; }
.toggle-row select { padding: 6px 8px; border-radius: 8px; border: 1px solid var(--line); background: var(--surface); }
.settings-actions { display: flex; flex-wrap: wrap; gap: 8px; padding-top: 14px; border-top: 1px solid var(--line); }
.dialog-foot { display: flex; justify-content: flex-end; margin-top: 18px; }
.toast {
  position: fixed; left: 50%; bottom: 24px; transform: translate(-50%, 20px);
  background: var(--text); color: var(--bg); padding: 10px 16px; border-radius: 10px;
  font-size: 14px; font-weight: 600; opacity: 0; pointer-events: none; transition: .25s ease; z-index: 50;
  max-width: calc(100vw - 32px);
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

@keyframes pop { 0% { transform: scale(.9); opacity: 0 } 100% { transform: scale(1); opacity: 1 } }
.pop { animation: pop .25s ease; }

/* ---------- responsive ---------- */
@media (max-width: 960px) {
  .menu-btn { display: grid; }
  .sidebar {
    position: fixed; top: 0; left: 0; bottom: 0; height: 100vh; z-index: 40;
    transform: translateX(-100%); transition: transform .25s ease; box-shadow: var(--shadow);
    width: min(var(--sidebar-w), 86vw);
  }
  .sidebar.open { transform: none; }
  .scrim.open { display: block; position: fixed; inset: 0; background: rgba(0, 0, 0, .35); z-index: 35; }
  .main { padding: 18px 16px 60px; }
}
@media (max-width: 640px) {
  .topbar { padding: 8px 16px; gap: 10px; flex-wrap: wrap; }
  .brand-sub, .brand-mark { display: none; }
  .brand { flex: 1; }
  .top-actions { margin-left: auto; }
  .overall { order: 5; max-width: none; flex-basis: 100%; }
  .overall-label { text-align: left; }
  h1.lec-title { font-size: 20px; }
  .card { padding: 18px 16px; }
  .question { font-size: 17px; }
  .result .score { font-size: 44px; }
}

[hidden] { display: none !important; }

/* ---------- auth ---------- */
.auth-screen { display: none; }
body.auth-mode .auth-screen {
  display: grid; place-items: center; min-height: 100vh; padding: 24px 16px;
  background: radial-gradient(circle at 20% 10%, var(--accent-soft), transparent 50%), var(--bg);
}
body.auth-mode .topbar, body.auth-mode .layout { display: none; }
.auth-card {
  width: min(400px, 100%); background: var(--surface); border: 1px solid var(--line);
  border-radius: 18px; box-shadow: var(--shadow); padding: 28px 26px;
}
.auth-brand { display: flex; align-items: center; gap: 10px; margin-bottom: 18px; }
.auth-form { display: grid; gap: 12px; }
.auth-form h1 { font-size: 20px; margin: 4px 0 2px; }
.auth-form label, .add-form label { display: grid; gap: 5px; font-size: 13px; font-weight: 600; color: var(--muted); }
.auth-form input, .add-form input {
  font-size: 16px; padding: 11px 12px; border-radius: 10px; border: 1.5px solid var(--line);
  background: var(--surface); color: var(--text); outline: none; width: 100%;
}
.auth-form input:focus, .add-form input:focus { border-color: var(--accent); }
.auth-form a, .small-note a { color: var(--accent-ink); font-weight: 600; }
.form-error { color: var(--bad); font-size: 14px; min-height: 1em; }
.small-note { font-size: 13px; margin: 0; }
.small { font-size: 12px; }

/* ---------- roles / views ---------- */
.teacher-only { display: none; }
body.role-teacher .teacher-only { display: inline-flex; }
body.view-dashboard .lecture-only,
body.view-dashboard #lectureList,
body.view-dashboard .sidebar,
body.view-dashboard .menu-btn,
body.view-dashboard .overall { display: none !important; }
body.role-teacher:not(.view-dashboard) #lectureViewBtn { display: none; }
body.view-dashboard #dashBtn { display: none; }
.user-chip { padding: 4px 12px 4px 4px; }
.avatar {
  width: 28px; height: 28px; border-radius: 50%; background: var(--accent); color: #fff;
  display: grid; place-items: center; font-size: 13px; font-weight: 800;
}
.account-info { display: grid; gap: 8px; margin-bottom: 12px; }
.account-info > div { display: flex; justify-content: space-between; gap: 10px; font-size: 14px; padding: 8px 0; border-bottom: 1px solid var(--line); }

/* ---------- teacher dashboard ---------- */
.container.wide { max-width: 1100px; }
.dash-head { display: flex; justify-content: space-between; align-items: flex-end; gap: 12px; flex-wrap: wrap; }
.dash-head a { color: var(--accent-ink); }
.dash-actions { display: flex; gap: 6px; flex-wrap: wrap; }
.add-form { display: grid; grid-template-columns: 1fr 1fr 1.4fr auto; gap: 10px; align-items: end; margin-top: 8px; }
.pw-row { display: flex; gap: 6px; }
.pw-row input { flex: 1; min-width: 0; font-family: ui-monospace, Consolas, monospace; }
.cred-box { margin-top: 14px; padding: 14px; border-radius: 12px; background: var(--good-soft); border: 1px solid color-mix(in srgb, var(--good) 30%, transparent); }
.cred-box pre { margin: 8px 0; padding: 10px 12px; background: var(--surface); border-radius: 8px; font-size: 14px; white-space: pre-wrap; font-family: ui-monospace, Consolas, monospace; }
.table-wrap { overflow-x: auto; margin: 6px -4px 0; }
.data-table { width: 100%; border-collapse: collapse; font-size: 14px; }
.data-table th { text-align: left; font-size: 12px; color: var(--muted); font-weight: 600; padding: 8px 10px; border-bottom: 1px solid var(--line); white-space: nowrap; }
.data-table td { padding: 10px; border-bottom: 1px solid var(--line); vertical-align: middle; }
.data-table .num { text-align: right; white-space: nowrap; }
.data-table tr.clickable { cursor: pointer; }
.data-table tr.clickable:hover td { background: var(--surface-2); }
.data-table .go { font-size: 20px; color: var(--muted); }
.data-table .sec-row td { background: var(--surface-2); font-weight: 700; font-size: 13px; color: var(--accent-ink); padding: 7px 10px; }
.progress-cell { min-width: 140px; }
.progress-cell .bar { margin-bottom: 3px; }
.bar-fill.done { background: var(--good); }
.watch-cell { white-space: nowrap; }
.bar.mini { display: inline-block; width: 60px; height: 6px; vertical-align: middle; margin-right: 6px; }
.tag.bad { background: var(--bad-soft); color: var(--bad); }
.wrong-list { margin: 6px 0 0; padding-left: 18px; font-size: 14px; }
.wrong-list li { margin: 4px 0; }
.wrong-list .ri-mine { color: var(--bad); }
details summary { cursor: pointer; color: var(--accent-ink); }
.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 12px; margin-top: 16px; }
.stat { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 16px; box-shadow: var(--shadow); }
.stat-label { font-size: 12px; color: var(--muted); font-weight: 600; }
.stat-value { font-size: 26px; font-weight: 800; margin: 2px 0 6px; }
.stat-value small { font-size: 14px; color: var(--muted); font-weight: 600; }
.stat-value.small-value { font-size: 15px; line-height: 1.4; }
@media (max-width: 760px) {
  .add-form { grid-template-columns: 1fr; }
  .user-chip #userName { display: none; }
  .user-chip { padding: 4px; }
}
.cred-box pre a { color: var(--accent-ink); font-weight: 700; }

/* ---------- 앱 전용 플레이어 (YouTube로 나가는 링크 차단) ---------- */
.player-shield {
  position: absolute; inset: 0; z-index: 2; cursor: pointer;
  display: grid; place-items: center; background: transparent; transition: background .2s;
  -webkit-tap-highlight-color: transparent; user-select: none;
}
.player-shield .big-play {
  width: 74px; height: 74px; border-radius: 50%; display: grid; place-items: center;
  background: var(--accent); color: #fff; font-size: 30px; padding-left: 5px;
  box-shadow: 0 6px 24px rgba(0, 0, 0, .35); opacity: 0; transform: scale(.9); transition: .2s;
}
/* 멈춤/종료 상태에서는 YouTube의 추천 영상·제목 위를 덮어 보이지 않게 */
.player-shield.paused { background: rgba(10, 8, 5, .55); }
.player-shield.paused .big-play { opacity: 1; transform: none; }
.player-wrap:fullscreen { aspect-ratio: auto; width: 100vw; height: 100vh; }
.player-wrap:-webkit-full-screen { aspect-ratio: auto; width: 100vw; height: 100vh; }
.pctrl {
  display: flex; align-items: center; gap: 8px; padding: 10px 12px;
  border-bottom: 1px solid var(--line); background: var(--surface-2);
}
.pc-btn {
  min-width: 38px; height: 34px; padding: 0 8px; border-radius: 8px; border: 1px solid var(--line);
  background: var(--surface); font-size: 14px; font-weight: 700; flex: none;
}
.pc-btn:hover { background: var(--accent-soft); }
#pcPlay { background: var(--accent); border-color: var(--accent); color: #fff; min-width: 44px; }
#pcSeek { flex: 1; min-width: 60px; accent-color: var(--accent); }
.pc-time { font-size: 12px; color: var(--muted); white-space: nowrap; font-variant-numeric: tabular-nums; }
#pcSpeed { height: 34px; border-radius: 8px; border: 1px solid var(--line); background: var(--surface); font-size: 13px; padding: 0 4px; }
@media (max-width: 520px) {
  .pctrl { flex-wrap: wrap; }
  #pcSeek { order: -1; flex-basis: 100%; }
  .pc-time { margin-right: auto; }
}
/* 휴대폰: 학생 목록은 핵심 열(학생·진도·오답·마지막 학습)만 */
@media (max-width: 640px) {
  .student-table th:nth-child(3), .student-table td:nth-child(3),
  .student-table th:nth-child(4), .student-table td:nth-child(4) { display: none; }
  .student-table td, .student-table th { padding: 9px 6px; }
  .progress-cell { min-width: 90px; }
  .data-table { font-size: 13px; }
}
.brand { min-width: 0; }
.brand > div { min-width: 0; }
.brand-title { overflow: hidden; text-overflow: ellipsis; }
@media (max-width: 640px) {
  .top-actions { gap: 6px; flex: none; }
  .top-actions .chip { padding: 6px 10px; font-size: 13px; }
  .pctrl { gap: 6px; padding: 8px 10px; }
  .pc-btn { min-width: 34px; padding: 0 6px; }
}
@media (max-width: 420px) { #pcBack { display: none; } }