:root {
  --ink: #17211f;
  --muted: #66716e;
  --line: #dce1dc;
  --paper: #fff;
  --wash: #f3f4f0;
  --forest: #173f3a;
  --forest-dark: #0f302c;
  --sage: #dce8df;
  --sand: #eee7da;
  --gold: #b68b57;
  --danger: #9a3f42;
  --radius: 22px;
  font-family: Pretendard, "Noto Sans KR", "Apple SD Gothic Neo", system-ui, sans-serif;
  color: var(--ink);
  background: var(--wash);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 320px; min-height: 100vh; background: var(--wash); }
body::before { content: ""; position: fixed; inset: 0; z-index: -1; pointer-events: none; background: linear-gradient(145deg, #fff9 0%, transparent 45%), radial-gradient(circle at 90% 6%, #dce6dcaa, transparent 28%); }
button, input, select, textarea { font: inherit; }
button { cursor: pointer; }
button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible { outline: 3px solid #b68b5759; outline-offset: 3px; }
.skip-link { position: fixed; top: -60px; left: 16px; z-index: 99; padding: 10px 14px; color: white; background: var(--forest); border-radius: 8px; }
.skip-link:focus { top: 12px; }
.site-header { width: min(1220px, calc(100% - 40px)); margin: 0 auto; min-height: 84px; display: flex; align-items: center; justify-content: space-between; gap: 18px; }
.brand { border: 0; background: transparent; display: flex; align-items: center; gap: 12px; color: var(--ink); text-align: left; padding: 0; }
.brand-mark { display: grid; place-items: center; width: 42px; height: 42px; color: white; font-family: Georgia, serif; font-size: 16px; font-weight: 700; letter-spacing: -.04em; border-radius: 50%; background: var(--forest); }
.brand strong, .brand small { display: block; }
.brand strong { font-size: 17px; letter-spacing: -.025em; }
.brand small { color: var(--muted); font-size: 10px; margin-top: 3px; letter-spacing: .08em; text-transform: uppercase; }
.header-actions { display: flex; align-items: center; gap: 10px; }
.header-link, .header-status { border: 1px solid var(--line); color: var(--ink); background: #ffffffb8; border-radius: 999px; padding: 9px 14px; font-size: 12px; font-weight: 750; backdrop-filter: blur(12px); }
.header-status { display: flex; align-items: center; gap: 7px; color: var(--muted); }
.status-dot { display: inline-block; width: 8px; height: 8px; border-radius: 50%; background: #98a19e; }
.status-dot.ok { background: #4b8a69; box-shadow: 0 0 0 4px #4b8a691c; }
.status-dot.bad { background: #a85b5e; }
main { width: min(1220px, calc(100% - 40px)); margin: 0 auto; padding: 26px 0 80px; }
.hero-premium { min-height: 655px; display: flex; align-items: center; overflow: hidden; border-radius: 30px; padding: 68px; background-image: linear-gradient(90deg, rgba(247,247,242,.99) 0%, rgba(247,247,242,.94) 36%, rgba(247,247,242,.48) 58%, rgba(247,247,242,.05) 80%), url("/static/hero-classroom-v2.png"); background-size: cover; background-position: center; box-shadow: 0 25px 80px #273d3630; }
.hero-copy { max-width: 660px; }
.eyebrow, .section-kicker { color: var(--forest); font-size: 11px; font-weight: 850; letter-spacing: .16em; }
h1 { font-size: clamp(40px, 6vw, 70px); line-height: 1.08; margin: 18px 0 22px; letter-spacing: -.055em; font-weight: 760; }
.hero p { max-width: 590px; color: #4f5b57; font-size: clamp(16px, 2vw, 19px); line-height: 1.75; margin: 0; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 32px; }
.primary, .secondary, .danger, .back { border-radius: 999px; padding: 13px 20px; font-weight: 800; transition: transform .18s, background .18s, box-shadow .18s; }
.primary { border: 1px solid var(--forest); background: var(--forest); color: white; box-shadow: 0 10px 24px #173f3a29; }
.primary:hover { background: var(--forest-dark); transform: translateY(-2px); }
.secondary, .back { border: 1px solid var(--line); background: white; color: var(--ink); }
.secondary:hover, .back:hover { border-color: #b7c1bb; transform: translateY(-2px); }
.danger { border: 0; background: #f5e4e4; color: var(--danger); }
.hero-primary, .hero-secondary { padding: 15px 23px; }
.hero-note { display: flex; align-items: center; gap: 12px; margin-top: 22px; color: var(--muted); font-size: 11px; }
.hero-note strong { color: var(--forest); }
.hero-note strong::after { content: ""; display: inline-block; width: 1px; height: 12px; margin-left: 12px; vertical-align: -2px; background: #b9c0bb; }
.mode-intro { display: grid; grid-template-columns: 1fr 1fr; gap: 50px; align-items: end; padding: 90px 6px 30px; }
.mode-intro h2 { margin: 12px 0 0; font-size: clamp(30px, 3.5vw, 42px); line-height: 1.22; letter-spacing: -.045em; }
.mode-intro p { color: var(--muted); line-height: 1.75; margin: 0; }
.mode-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.mode-card { position: relative; min-height: 340px; border: 1px solid var(--line); border-radius: 26px; background: #fff; padding: 34px; color: var(--ink); text-align: left; overflow: hidden; transition: transform .25s, box-shadow .25s; }
.mode-card:hover { transform: translateY(-5px); box-shadow: 0 24px 60px #263b3420; }
.mode-featured { color: white; border-color: var(--forest); background: var(--forest); }
.mode-index { position: absolute; top: 28px; right: 32px; font-family: Georgia, serif; font-size: 54px; color: #17211f13; }
.mode-featured .mode-index { color: #ffffff17; }
.mode-label { font-size: 10px; letter-spacing: .16em; font-weight: 800; color: var(--gold); }
.mode-card h3 { max-width: 510px; margin: 62px 0 14px; font-size: clamp(25px, 3vw, 34px); line-height: 1.3; letter-spacing: -.04em; }
.mode-card p { max-width: 500px; color: var(--muted); line-height: 1.7; }
.mode-featured p { color: #d6e0dc; }
.text-link { position: absolute; bottom: 32px; left: 34px; color: inherit; font-size: 13px; font-weight: 850; }
.text-link span { margin-left: 8px; }
.principles { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0; margin-top: 22px; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.principles > div { padding: 28px 25px; border-right: 1px solid var(--line); }
.principles > div:last-child { border-right: 0; }
.principles span { color: var(--gold); font-size: 11px; font-weight: 850; letter-spacing: .1em; }
.principles strong { display: block; margin: 11px 0 7px; font-size: 16px; }
.principles p { margin: 0; color: var(--muted); font-size: 13px; line-height: 1.6; }
.page-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 20px; margin: 28px 0 28px; }
.page-head h1 { font-size: clamp(34px, 5vw, 54px); margin: 0; }
.page-head .hint { margin-top: 9px; }
.back { flex: none; padding: 10px 15px; }
.actual-intro { max-width: 740px; margin: 36px 0 28px; }
.actual-intro h2 { margin: 17px 0 10px; font-size: 28px; letter-spacing: -.035em; }
.actual-intro p { margin: 0; color: var(--muted); line-height: 1.7; }
.live-pill { display: inline-flex; align-items: center; gap: 8px; padding: 7px 11px; border: 1px solid var(--line); border-radius: 999px; background: white; font-size: 11px; font-weight: 800; }
.choice-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.choice { position: relative; min-height: 285px; overflow: hidden; border: 1px solid var(--line); border-radius: 22px; background: white; padding: 27px; text-align: left; transition: transform .2s, box-shadow .2s, border .2s; }
.choice:hover { transform: translateY(-4px); border-color: #aab6af; box-shadow: 0 20px 50px #263b341c; }
.choice-icon { display: grid; place-items: center; width: 46px; height: 46px; border-radius: 50%; color: white; background: var(--forest); font-family: Georgia, serif; font-size: 13px; }
.choice-overline { display: block; margin-top: 20px; color: var(--gold); font-size: 9px; font-weight: 850; letter-spacing: .16em; }
.choice h2 { margin: 10px 0 9px; font-size: 23px; letter-spacing: -.03em; }
.choice p { margin: 0; color: var(--muted); line-height: 1.65; font-size: 14px; }
.choice .arrow { position: absolute; right: 25px; bottom: 22px; color: var(--forest); font-size: 22px; }
.truth-note { display: grid; grid-template-columns: 180px 1fr; gap: 22px; margin-top: 20px; padding: 22px 24px; border-radius: 16px; background: var(--sand); }
.truth-note p { margin: 0; color: #5e625d; font-size: 13px; line-height: 1.65; }
.panel { border: 1px solid var(--line); border-radius: var(--radius); background: #fffffff2; padding: 28px; box-shadow: 0 14px 45px #263b340e; }
.form-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 18px; }
.field { display: grid; gap: 8px; }
.field.full { grid-column: 1 / -1; }
.field label, .demo-form label span, .student-join-preview label span, .submission-preview > span { font-size: 12px; font-weight: 850; }
.hint { color: var(--muted); font-size: 12px; line-height: 1.5; }
input, select, textarea { width: 100%; border: 1px solid var(--line); border-radius: 12px; background: white; color: var(--ink); padding: 13px 14px; outline: 0; }
textarea { min-height: 120px; resize: vertical; line-height: 1.65; }
input:focus, select:focus, textarea:focus { border-color: var(--forest); box-shadow: 0 0 0 4px #173f3a12; }
input[readonly], textarea[readonly] { color: #35413d; background: #fbfbf8; }
.actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 18px; }
.dashboard-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.room-banner { grid-column: 1 / -1; color: white; background: linear-gradient(135deg, var(--forest), #2b5d54); }
.room-code { font-family: Georgia, serif; font-size: clamp(42px, 10vw, 72px); font-weight: 700; letter-spacing: .12em; line-height: 1; margin: 12px 0; }
.room-banner p { color: #dce7e2; margin: 5px 0; }
.room-banner .secondary { color: var(--forest); }
.mini-title { margin: 0 0 14px; font-size: 18px; }
.stack { display: grid; gap: 12px; }
.item { border: 1px solid var(--line); border-radius: 14px; padding: 15px; background: white; }
.item h3 { font-size: 15px; margin: 0 0 5px; }
.item p { color: var(--muted); font-size: 13px; line-height: 1.6; margin: 0; white-space: pre-wrap; }
.badge { display: inline-flex; align-items: center; border-radius: 999px; background: var(--sage); color: var(--forest); font-size: 10px; font-weight: 850; padding: 5px 8px; margin-bottom: 8px; }
.empty { color: var(--muted); text-align: center; padding: 24px 8px; font-size: 13px; }
.notice { border-left: 3px solid var(--gold); background: #f8f4ec; border-radius: 9px; padding: 12px 14px; font-size: 13px; line-height: 1.5; }
.ai-answer { margin-top: 14px; padding: 19px; border-radius: 14px; background: #edf4f0; border: 1px solid #d5e2db; white-space: pre-wrap; line-height: 1.75; }
.ai-answer small { display: block; color: var(--muted); margin-top: 12px; }
.activity-work { display: grid; gap: 12px; margin-top: 12px; }
.join-card { max-width: 600px; margin: 0 auto; }
.demo-header { display: flex; justify-content: space-between; align-items: flex-start; gap: 24px; padding: 28px 0 25px; }
.demo-header h1 { margin: 13px 0 10px; font-size: clamp(34px, 5vw, 55px); }
.demo-header p { max-width: 720px; margin: 0; color: var(--muted); line-height: 1.65; }
.demo-badge, .simulation-label { display: inline-flex; width: max-content; padding: 6px 9px; border-radius: 999px; color: #795b36; background: #f1e7d7; font-size: 9px; font-weight: 900; letter-spacing: .14em; }
.demo-progress { display: grid; grid-template-columns: repeat(6, 1fr); list-style: none; margin: 20px 0; padding: 0; border: 1px solid var(--line); border-radius: 15px; background: #ffffff9e; overflow: hidden; }
.demo-progress li { position: relative; display: flex; align-items: center; gap: 8px; min-width: 0; padding: 13px 12px; color: #8a928f; border-right: 1px solid var(--line); }
.demo-progress li:last-child { border-right: 0; }
.demo-progress span { font-family: Georgia, serif; font-size: 12px; }
.demo-progress em { overflow: hidden; font-size: 11px; font-style: normal; font-weight: 750; text-overflow: ellipsis; white-space: nowrap; }
.demo-progress li.done { color: #678078; background: #eef3ef; }
.demo-progress li.active { color: white; background: var(--forest); }
.demo-canvas { display: grid; grid-template-columns: minmax(0, 1.7fr) minmax(240px, .55fr); min-height: 530px; overflow: hidden; border-radius: 26px; color: var(--ink); background: white; box-shadow: 0 24px 65px #253a3326; }
.demo-stage { padding: clamp(28px, 5vw, 54px); }
.demo-stage-head { display: flex; align-items: center; justify-content: space-between; gap: 15px; margin-bottom: 30px; }
.role-label { padding: 7px 10px; border-radius: 999px; color: white; background: var(--forest); font-size: 10px; font-weight: 850; letter-spacing: .08em; }
.student-role { color: var(--forest); background: var(--sage); }
.scene-time, .live-sim { color: var(--muted); font-size: 11px; font-weight: 800; }
.live-sim { display: flex; align-items: center; gap: 7px; }
.live-sim i { width: 7px; height: 7px; border-radius: 50%; background: #4b8a69; box-shadow: 0 0 0 4px #4b8a6919; }
.demo-stage > h2 { max-width: 760px; margin: 0 0 10px; font-size: clamp(26px, 4vw, 39px); line-height: 1.3; letter-spacing: -.04em; }
.demo-stage > p { color: var(--muted); line-height: 1.65; }
.demo-aside { display: flex; flex-direction: column; justify-content: flex-end; padding: 38px 30px; color: white; background: var(--forest); }
.aside-index { color: #d7bc98; font-family: Georgia, serif; font-size: 11px; letter-spacing: .12em; }
.demo-aside h3 { margin: 16px 0 10px; font-size: 23px; line-height: 1.35; letter-spacing: -.03em; }
.demo-aside p { margin: 0; color: #d9e4df; font-size: 13px; line-height: 1.7; }
.demo-form { display: grid; grid-template-columns: 1fr 1fr; gap: 15px; margin-top: 28px; }
.demo-form label, .student-join-preview label, .submission-preview { display: grid; gap: 7px; }
.demo-form .wide { grid-column: 1 / -1; }
.demo-form textarea { min-height: 82px; }
.demo-room { display: flex; flex-direction: column; align-items: flex-start; justify-content: center; color: white; background: linear-gradient(135deg, #244c45, #173f3a); }
.demo-room .demo-stage-head { width: 100%; }
.demo-room .demo-caption { color: #cbd9d4; font-size: 12px; }
.demo-code { margin: 2px 0 22px; font-family: Georgia, serif; font-size: clamp(50px, 9vw, 82px); letter-spacing: .13em; }
.demo-room h2 { color: white; }
.activity-preview { width: 100%; margin-top: 23px; padding: 18px; border: 1px solid var(--line); border-radius: 14px; background: #f8f8f4; color: var(--ink); }
.demo-room .activity-preview { border-color: #ffffff24; background: #ffffff0e; color: white; }
.activity-preview span { display: block; margin-bottom: 7px; color: var(--gold); font-size: 10px; font-weight: 850; letter-spacing: .1em; text-transform: uppercase; }
.activity-preview strong { display: block; font-size: 17px; }
.activity-preview p { margin: 8px 0 0; color: var(--muted); font-size: 13px; line-height: 1.55; }
.demo-room .activity-preview p { color: #dbe5e1; }
.student-join-preview { display: grid; gap: 14px; max-width: 570px; margin-top: 30px; }
.student-join-preview input { font-size: 17px; font-weight: 800; }
.join-confirm { display: grid; gap: 4px; margin-top: 6px; padding: 16px; border-radius: 12px; color: var(--forest); background: var(--sage); }
.join-confirm span { font-size: 12px; }
.demo-chat { display: grid; gap: 13px; margin-top: 25px; }
.demo-chat > div { max-width: 90%; padding: 15px 17px; border-radius: 14px; }
.demo-chat span { display: block; margin-bottom: 7px; font-size: 10px; font-weight: 850; }
.demo-chat p { margin: 0; white-space: pre-line; line-height: 1.62; font-size: 13px; }
.chat-user { justify-self: end; color: white; background: var(--forest); }
.chat-ai { background: #eef3ef; }
.demo-disclosure { display: flex; flex-wrap: wrap; gap: 7px 12px; margin-top: 14px; color: #785d3c; font-size: 10px; }
.submission-preview { margin-top: 16px; }
.submission-preview textarea { min-height: 110px; }
.demo-metrics { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 27px 0 18px; }
.demo-metrics div { display: grid; gap: 4px; padding: 18px; border-radius: 13px; background: #eef3ef; }
.demo-metrics strong { color: var(--forest); font-family: Georgia, serif; font-size: 30px; }
.demo-metrics span { color: var(--muted); font-size: 11px; }
.review-card { border: 1px solid var(--line); border-radius: 15px; padding: 18px; }
.review-card > div { display: flex; justify-content: space-between; gap: 15px; }
.review-card em { color: #4b7a64; font-size: 11px; font-style: normal; font-weight: 850; }
.review-card p { color: #46514d; line-height: 1.65; font-size: 13px; }
.review-card footer { margin: 14px -18px -18px; padding: 14px 18px; border-radius: 0 0 14px 14px; background: #f3eee4; color: #675d4f; font-size: 12px; line-height: 1.55; }
.review-card footer strong { display: block; margin-bottom: 4px; color: #765b38; }
.demo-controls { display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 20px 4px 0; }
.demo-controls > div:first-child { display: flex; align-items: baseline; gap: 10px; }
.demo-controls > div:first-child strong { font-family: Georgia, serif; font-size: 17px; }
.demo-controls > div:first-child span { color: var(--muted); font-size: 12px; }
.demo-controls .actions { margin-top: 0; }
.toast { position: fixed; z-index: 90; right: 18px; bottom: 18px; max-width: min(420px, calc(100% - 36px)); transform: translateY(140%); opacity: 0; transition: .25s; border-radius: 12px; background: var(--ink); color: white; padding: 13px 16px; box-shadow: 0 16px 40px #17213e55; }
.toast.show { transform: translateY(0); opacity: 1; }
.toast.error { background: var(--danger); }
.loader { display: inline-block; width: 16px; height: 16px; border: 2px solid #ffffff66; border-top-color: white; border-radius: 50%; animation: spin .7s linear infinite; vertical-align: -3px; margin-right: 7px; }
@keyframes spin { to { transform: rotate(360deg); } }
@media (max-width: 900px) {
  .hero-premium { min-height: 620px; padding: 48px; background-position: 58% center; }
  .mode-intro { grid-template-columns: 1fr; gap: 18px; }
  .choice-grid, .dashboard-grid { grid-template-columns: 1fr; }
  .choice { min-height: 240px; }
  .room-banner { grid-column: auto; }
  .demo-canvas { grid-template-columns: 1fr; }
  .demo-aside { min-height: 210px; }
}
@media (max-width: 680px) {
  .site-header, main { width: min(100% - 24px, 1220px); }
  .site-header { min-height: 72px; }
  .brand small, #ai-status { display: none; }
  .header-actions { gap: 6px; }
  .header-link, .header-status { padding: 8px 10px; }
  main { padding-top: 10px; }
  .hero-premium { min-height: 650px; align-items: flex-end; border-radius: 20px; padding: 28px 23px; background-image: linear-gradient(0deg, rgba(246,246,241,.98) 0%, rgba(246,246,241,.93) 48%, rgba(246,246,241,.15) 82%), url("/static/hero-classroom-v2.png"); background-position: 62% center; }
  h1 { font-size: 40px; }
  .hero p { font-size: 15px; }
  .hero-actions { display: grid; }
  .hero-note { display: grid; gap: 5px; }
  .hero-note strong::after { display: none; }
  .mode-intro { padding-top: 62px; }
  .mode-grid, .principles { grid-template-columns: 1fr; }
  .mode-card { min-height: 315px; padding: 28px; }
  .principles > div { border-right: 0; border-bottom: 1px solid var(--line); }
  .principles > div:last-child { border-bottom: 0; }
  .truth-note { grid-template-columns: 1fr; gap: 7px; }
  .form-grid, .demo-form { grid-template-columns: 1fr; }
  .field.full, .demo-form .wide { grid-column: auto; }
  .panel { padding: 20px; }
  .page-head, .demo-header, .demo-controls { align-items: flex-start; flex-direction: column-reverse; }
  .demo-header { padding-top: 18px; }
  .demo-progress { display: flex; overflow-x: auto; }
  .demo-progress li { flex: 0 0 auto; min-width: 92px; }
  .demo-progress em { display: none; }
  .demo-canvas { min-height: 0; border-radius: 20px; }
  .demo-stage { padding: 25px 20px; }
  .demo-aside { padding: 28px 22px; min-height: 180px; }
  .demo-stage-head { margin-bottom: 22px; }
  .demo-chat > div { max-width: 100%; }
  .demo-metrics { grid-template-columns: 1fr 1fr; }
  .demo-metrics div:last-child { grid-column: 1 / -1; }
  .demo-controls { flex-direction: column; }
  .demo-controls .actions { width: 100%; }
  .demo-controls .actions button { flex: 1; }
  .room-code { letter-spacing: .07em; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
}