/* =====================================================
   Aiin AI Tutor — Landing Page
   ===================================================== */

:root {
  --bg: #ffffff;
  --bg-soft: #f6f6f8;
  --bg-dark: #0a0a0c;
  --bg-dark-soft: #15151a;
  --text: #0a0a0c;
  --text-soft: #5b5b62;
  --text-muted: #9a9aa0;
  --text-on-dark: #f5f5f7;
  --text-on-dark-soft: #a8a8b0;
  --border: #ececef;
  --border-dark: #2a2a30;
  --accent: #6366f1;
  --accent-soft: #eef0ff;
  --accent-dark: #4f52d6;
  --ko: #ef4444;
  --en: #3b82f6;
  --radius: 14px;
  --radius-lg: 22px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.04), 0 2px 8px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.06), 0 12px 32px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 40px rgba(0,0,0,0.10);
  --max: 1200px;
  --space: clamp(60px, 8vw, 110px);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: 'Pretendard', 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font: inherit; cursor: pointer; border: none; background: transparent; }

.container {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 24px;
}

/* =====================================================
   Nav
   ===================================================== */

.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  border-bottom: 1px solid rgba(0,0,0,0.06);
}
.nav-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 16px;
  letter-spacing: -0.01em;
}
.logo-mark { color: var(--accent); font-size: 22px; line-height: 1; }
.logo-text { color: var(--text); }
.logo-divider { color: var(--text-muted); font-weight: 400; }
.logo-project { color: var(--text-soft); font-weight: 500; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  font-size: 14px;
  font-weight: 500;
}
.nav-links a {
  color: var(--text-soft);
  transition: color 0.15s;
}
.nav-links a:hover { color: var(--text); }
.nav-cta {
  background: var(--text);
  color: var(--bg) !important;
  padding: 9px 16px;
  border-radius: 999px;
  font-weight: 600;
}
.nav-cta:hover { background: var(--accent); color: var(--bg) !important; }

@media (max-width: 720px) {
  .nav-links a:not(.nav-cta) { display: none; }
}

/* =====================================================
   Hero
   ===================================================== */

.hero {
  padding-top: 60px;
  min-height: min(100vh, 760px);
  display: flex;
  align-items: stretch;
  background-color: #ffffff;
  background-image:
    radial-gradient(circle at 20% 0%, rgba(99,102,241,0.07), transparent 50%),
    radial-gradient(circle at 80% 30%, rgba(239,68,68,0.04), transparent 40%);
  overflow: hidden;
  position: relative;
}
/* Hero 이미지 — 통이미지(원본 비율) 그대로 우측 정렬 */
.hero-images {
  position: absolute;
  top: 60px;
  right: 0;
  left: 0;
  bottom: 0;
  pointer-events: none;
  z-index: 1;
  overflow: hidden;
}
/* 좌측 텍스트 가독성 보장 — 좌측 30%에 흰색 페이드 */
.hero-images::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(to right, #ffffff 0%, #ffffff 28%, rgba(255,255,255,0) 50%);
  z-index: 2;
  pointer-events: none;
}
.hero-img {
  position: absolute;
  top: 0;
  right: 0;
  height: auto;
  width: auto;
  max-width: 65%;
  max-height: 100%;
  opacity: 0;
  transition: opacity 0.7s ease;
}
@media (max-width: 980px) {
  .hero-img {
    max-width: 100%;
    max-height: none;
    width: 100%;
    bottom: 0;
    top: auto;
  }
}
.hero-img.active { opacity: 1; }
@media (max-width: 980px) {
  .hero-img { object-position: right center; opacity: 0; }
  .hero-img.active { opacity: 0.4; }
}
.hero-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 60px 24px 0;
  width: 100%;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  position: relative;
  z-index: 2;
}
.hero-slide {
  max-width: 56%;
}
@media (max-width: 980px) {
  .hero-slide { max-width: 100%; }
}

.hero-slide {
  display: none;
  animation: fadeIn 0.6s ease;
}
.hero-slide.active { display: block; max-width: 56%; }
@media (max-width: 980px) {
  .hero-slide.active { max-width: 100%; }
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.hero-flag {
  display: inline-block;
  padding: 6px 14px;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  margin-bottom: 24px;
}
.hero-slide[data-slide="en"] .hero-flag {
  background: rgba(59, 130, 246, 0.1);
  color: var(--en);
}

.hero-title {
  font-size: clamp(40px, 6.5vw, 80px);
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -0.03em;
  margin-bottom: 24px;
}
.hero-title-accent {
  background: linear-gradient(135deg, var(--accent) 0%, #8b5cf6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-sub {
  font-size: clamp(16px, 1.5vw, 19px);
  color: var(--text-soft);
  line-height: 1.6;
  margin-bottom: 40px;
  max-width: 580px;
}

.hero-cta-row {
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 16px 28px;
  background: var(--text);
  color: var(--bg);
  border-radius: 999px;
  font-weight: 600;
  font-size: 16px;
  transition: transform 0.15s, background 0.15s;
}
.btn-primary:hover {
  background: var(--accent);
  transform: translateY(-1px);
}
.btn-primary .btn-arrow {
  transition: transform 0.2s;
}
.btn-primary:hover .btn-arrow { transform: translateX(3px); }
.btn-lg { padding: 20px 36px; font-size: 17px; }

.hero-meta {
  font-size: 13px;
  color: var(--text-muted);
}

.hero-indicator {
  position: absolute;
  top: 100px;
  left: 24px;
  display: flex;
  flex-direction: row;
  gap: 8px;
  z-index: 4;
}
.hero-dot {
  width: 28px;
  height: 6px;
  border-radius: 3px;
  background: rgba(0,0,0,0.15);
  transition: background 0.2s, width 0.2s;
  cursor: pointer;
}
.hero-dot.active {
  background: var(--text);
  width: 40px;
}

/* Hero marquee */
.hero-marquee {
  margin-top: 60px;
  overflow: hidden;
  mask-image: linear-gradient(to right, transparent, black 8%, black 92%, transparent);
  -webkit-mask-image: linear-gradient(to right, transparent, black 8%, black 92%, transparent);
  padding: 12px 0 24px;
  position: relative;
  z-index: 3;
}
.marquee-track {
  display: flex;
  gap: 14px;
  animation: marquee 60s linear infinite;
  width: max-content;
}
@keyframes marquee {
  from { transform: translateX(0); }
  to   { transform: translateX(-50%); }
}
.marquee-card {
  flex: 0 0 130px;
  height: 130px;
  width: 130px;
  border-radius: 50%;
  background: var(--bg-soft);
  border: 3px solid var(--border);
  overflow: hidden;
  position: relative;
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s;
  cursor: pointer;
  text-decoration: none;
}
.marquee-card img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.marquee-card .marquee-name {
  position: absolute;
  inset: auto 0 0 0;
  padding: 24px 6px 8px;
  font-size: 13px;
  font-weight: 700;
  color: #fff;
  text-align: center;
  background: linear-gradient(to top, rgba(0,0,0,0.7), transparent);
  opacity: 0;
  transition: opacity 0.2s;
}
.marquee-card:hover {
  transform: scale(1.1);
  border-color: var(--accent);
  box-shadow: 0 6px 16px rgba(99,102,241,0.25);
}
.marquee-card:hover .marquee-name { opacity: 1; }
.marquee-card.en { border-color: rgba(59,130,246,0.3); }
.marquee-card.en:hover { border-color: var(--en); box-shadow: 0 6px 16px rgba(59,130,246,0.25); }

/* =====================================================
   Features
   ===================================================== */

.features {
  padding: var(--space) 0;
  background: var(--bg-soft);
}
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.feature {
  background: var(--bg);
  padding: 36px 28px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.feature-num {
  font-size: 56px;
  font-weight: 800;
  letter-spacing: -0.04em;
  background: linear-gradient(135deg, var(--accent) 0%, #8b5cf6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  margin-bottom: 16px;
}
.feature-title {
  font-size: 19px;
  font-weight: 700;
  margin-bottom: 10px;
  letter-spacing: -0.01em;
}
.feature-desc {
  font-size: 15px;
  color: var(--text-soft);
  line-height: 1.65;
}

@media (max-width: 820px) {
  .features-grid { grid-template-columns: 1fr; }
}

/* =====================================================
   Galleries (Korean / English)
   ===================================================== */

.gallery {
  padding: var(--space) 0;
}
.gallery-ko { background: var(--bg); }
.gallery-en { background: var(--bg-soft); }

.section-head {
  text-align: center;
  max-width: 720px;
  margin: 0 auto 56px;
}
.section-flag {
  display: inline-block;
  padding: 6px 14px;
  background: rgba(239,68,68,0.08);
  color: var(--ko);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  margin-bottom: 20px;
}
.gallery-en .section-flag {
  background: rgba(59,130,246,0.08);
  color: var(--en);
}
.section-flag.dark {
  background: rgba(99,102,241,0.15);
  color: #a5a8ff;
}
.section-title {
  font-size: clamp(28px, 4vw, 44px);
  font-weight: 800;
  letter-spacing: -0.025em;
  margin-bottom: 14px;
  line-height: 1.15;
}
.section-sub {
  font-size: 17px;
  color: var(--text-soft);
  line-height: 1.6;
}
.section-head.dark .section-title { color: var(--text-on-dark); }
.section-head.dark .section-sub { color: var(--text-on-dark-soft); }

.tutors-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.tutor-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 22px;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}
.gallery-en .tutor-card { background: var(--bg); }
.tutor-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
}

.tutor-avatar {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  background: linear-gradient(135deg, #f0f0f5, #e5e5ee);
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 32px;
  font-weight: 700;
  color: var(--text-muted);
  overflow: hidden;
  position: relative;
}
.tutor-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.tutor-avatar.placeholder::after {
  content: '';
  position: absolute;
  inset: 0;
  border: 2px dashed rgba(0,0,0,0.08);
  border-radius: 50%;
}

.tutor-name {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
}
.tutor-name-sub {
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 10px;
  font-family: 'Inter', sans-serif;
  letter-spacing: 0.03em;
}
.tutor-tag {
  font-size: 12px;
  padding: 4px 10px;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 999px;
  font-weight: 600;
  margin-bottom: 12px;
}
.gallery-en .tutor-tag {
  background: rgba(59,130,246,0.1);
  color: var(--en);
}
.tutor-desc {
  font-size: 13px;
  color: var(--text-soft);
  line-height: 1.55;
  margin-bottom: 16px;
  min-height: 40px;
}
.tutor-cta {
  margin-top: auto;
  width: 100%;
  padding: 10px 14px;
  background: var(--bg-soft);
  color: var(--text);
  border-radius: 10px;
  font-weight: 600;
  font-size: 14px;
  transition: background 0.15s, color 0.15s;
}
.tutor-card:hover .tutor-cta {
  background: var(--text);
  color: var(--bg);
}

@media (max-width: 980px) {
  .tutors-grid { grid-template-columns: repeat(3, 1fr); }
}
@media (max-width: 720px) {
  .tutors-grid { grid-template-columns: repeat(2, 1fr); }
  .tutor-avatar { width: 90px; height: 90px; }
}
@media (max-width: 480px) {
  .tutors-grid { grid-template-columns: 1fr; }
  .tutor-card { flex-direction: row; text-align: left; align-items: center; gap: 16px; padding: 16px; }
  .tutor-avatar { margin-bottom: 0; flex: 0 0 64px; width: 64px; height: 64px; }
  .tutor-desc { min-height: 0; margin-bottom: 8px; }
  .tutor-cta { width: auto; padding: 6px 12px; font-size: 12px; }
}

/* =====================================================
   Tech Section (Dark)
   ===================================================== */

.tech {
  padding: var(--space) 0;
  background: var(--bg-dark);
  color: var(--text-on-dark);
}
.tech-pipeline {
  display: flex;
  align-items: stretch;
  justify-content: center;
  gap: 14px;
  margin-bottom: 80px;
  flex-wrap: wrap;
}
.tech-diagram {
  display: block;
  width: 100%;
  max-width: 1100px;
  height: auto;
  margin: 0 auto 80px;
  border-radius: var(--radius-lg);
  box-shadow: 0 0 100px rgba(139, 92, 246, 0.25);
}

/* 체험 흐름 섹션 */
.flow {
  padding: 60px 0 var(--space);
  background: var(--bg);
}
.flow-diagram {
  display: block;
  width: 100%;
  max-width: 1100px;
  height: auto;
  margin: 0 auto;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}
.tech-block {
  flex: 1;
  min-width: 180px;
  max-width: 240px;
  background: var(--bg-dark-soft);
  border: 1px solid var(--border-dark);
  border-radius: var(--radius);
  padding: 24px 20px;
  text-align: center;
}
.tech-icon {
  font-size: 28px;
  margin-bottom: 12px;
}
.tech-label {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: 8px;
}
.tech-name {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 6px;
}
.tech-meta {
  font-size: 12px;
  color: var(--text-on-dark-soft);
  line-height: 1.5;
}
.tech-arrow {
  display: flex;
  align-items: center;
  color: var(--text-on-dark-soft);
  font-size: 22px;
  font-weight: 300;
}

.tech-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  border-top: 1px solid var(--border-dark);
  padding-top: 60px;
}
.stat {
  text-align: center;
}
.stat-num {
  font-size: clamp(32px, 4vw, 52px);
  font-weight: 800;
  letter-spacing: -0.04em;
  background: linear-gradient(135deg, #c4c5ff 0%, #8b5cf6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
  margin-bottom: 8px;
}
.stat-label {
  font-size: 13px;
  color: var(--text-on-dark-soft);
  letter-spacing: 0.02em;
}

@media (max-width: 720px) {
  .tech-arrow { transform: rotate(90deg); margin: 4px 0; }
  .tech-pipeline { flex-direction: column; align-items: center; }
  .tech-block { width: 100%; max-width: 320px; }
  .tech-stats { grid-template-columns: repeat(2, 1fr); }
}

/* =====================================================
   Contact / B2B
   ===================================================== */

.contact {
  padding: var(--space) 0;
  background: var(--bg);
}
.contact-card {
  background: linear-gradient(135deg, #1a1a23 0%, #2d1f4a 100%);
  border-radius: var(--radius-lg);
  padding: clamp(40px, 6vw, 72px);
  display: grid;
  grid-template-columns: 1.4fr 1fr;
  gap: 48px;
  align-items: center;
  color: var(--text-on-dark);
}
.contact-tag {
  display: inline-block;
  padding: 5px 12px;
  background: rgba(255,255,255,0.1);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  margin-bottom: 20px;
}
.contact-text h2 {
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}
.contact-text p {
  font-size: 16px;
  color: var(--text-on-dark-soft);
  line-height: 1.7;
}
.contact-actions {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 16px;
}
.contact-actions .btn-primary {
  background: var(--bg);
  color: var(--text);
}
.contact-actions .btn-primary:hover {
  background: var(--accent);
  color: var(--bg);
}
.contact-meta {
  font-size: 13px;
  color: var(--text-on-dark-soft);
  line-height: 1.6;
}

@media (max-width: 820px) {
  .contact-card { grid-template-columns: 1fr; gap: 24px; }
}

/* =====================================================
   Footer
   ===================================================== */

.footer {
  padding: 60px 0 40px;
  background: var(--bg-soft);
  border-top: 1px solid var(--border);
}
.footer-inner {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr;
  gap: 40px;
}
.footer-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
}
.footer-tag {
  font-size: 14px;
  color: var(--text-soft);
  margin-bottom: 16px;
  line-height: 1.55;
}
.footer-link {
  font-size: 14px;
  color: var(--accent);
  font-weight: 600;
}
.footer-col-title {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 14px;
}
.footer-projects, .footer-meta {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.footer-projects a, .footer-meta a {
  font-size: 14px;
  color: var(--text-soft);
  transition: color 0.15s;
}
.footer-projects a:hover, .footer-meta a:hover { color: var(--text); }
.footer-copy {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 14px;
}

@media (max-width: 720px) {
  .footer-inner { grid-template-columns: 1fr; gap: 28px; }
}