/* ============================================
   Brain180 — Design System & Styles
   ============================================ */

/* --- CSS Custom Properties --- */
:root {
  /* Backgrounds */
  --bg-primary: #0A0A0F;
  --bg-surface: #12121A;
  --bg-elevated: #1A1A2E;

  /* Borders */
  --border-subtle: #2A2A3E;
  --border-hover: #3B3B5E;

  /* Text */
  --text-primary: #F0F0F5;
  --text-secondary: #9898B0;
  --text-muted: #6B6B80;

  /* Accent — Gold */
  --accent-primary: #D4A853;
  --accent-hover: #E8C06A;
  --accent-glow: rgba(212, 168, 83, 0.15);

  /* CTA — Blue */
  --cta-primary: #4A6CF7;
  --cta-hover: #5B7DF8;
  --cta-glow: rgba(74, 108, 247, 0.2);

  /* Semantic */
  --success: #34D399;
  --info: #60A5FA;

  /* Gradients */
  --gradient-hero: linear-gradient(135deg, #0A0A0F 0%, #1A1034 50%, #0A0A0F 100%);
  --gradient-accent: linear-gradient(135deg, #D4A853, #E8C06A, #D4A853);
  --gradient-neural: linear-gradient(135deg, #4A6CF7 0%, #7C3AED 50%, #4A6CF7 100%);

  /* Spacing */
  --section-padding: 120px;
  --section-padding-mobile: 80px;
  --container-max: 1200px;
  --nav-height: 72px;

  /* Transitions */
  --ease-default: cubic-bezier(0.4, 0, 0.2, 1);
  --ease-out: cubic-bezier(0, 0, 0.2, 1);
}

/* --- Reset & Base --- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Noto Sans KR', sans-serif;
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  word-break: keep-all;
  overflow-x: hidden;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

img {
  max-width: 100%;
  display: block;
}

button {
  border: none;
  background: none;
  cursor: pointer;
  font-family: inherit;
  color: inherit;
}

input, select, textarea {
  font-family: inherit;
  font-size: 16px; /* Prevents iOS zoom on focus */
}

/* --- Loader --- */
.loader {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--bg-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.5s var(--ease-default), visibility 0.5s;
}

.loader.hidden {
  opacity: 0;
  visibility: hidden;
}

.loader-logo {
  font-family: 'Inter', sans-serif;
  font-size: 32px;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  animation: loaderPulse 1.5s ease-in-out infinite;
}

.loader-accent {
  background: var(--gradient-neural);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

@keyframes loaderPulse {
  0%, 100% { opacity: 0.4; }
  50% { opacity: 1; }
}

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

/* --- Typography --- */
.section-label {
  display: block;
  font-family: 'Inter', sans-serif;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 3px;
  text-transform: uppercase;
  color: var(--accent-primary);
  margin-bottom: 16px;
}

.section-title {
  font-size: 40px;
  font-weight: 700;
  line-height: 1.3;
  color: var(--text-primary);
  margin-bottom: 24px;
}

.section-intro {
  font-size: 18px;
  line-height: 1.8;
  color: var(--text-secondary);
  max-width: 720px;
  margin-bottom: 64px;
}

.en-term {
  font-family: 'Inter', sans-serif;
  font-weight: 500;
  color: var(--text-muted);
  font-size: 0.9em;
}

.text-accent {
  color: var(--accent-primary);
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: 6px;
  font-size: 16px;
  font-weight: 500;
  transition: all 150ms var(--ease-default);
  cursor: pointer;
  white-space: nowrap;
}

.btn-primary {
  background: var(--cta-primary);
  color: #fff;
  box-shadow: 0 0 0 0 var(--cta-glow);
}

.btn-primary:hover {
  background: var(--cta-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 20px var(--cta-glow);
}

.btn-primary:active {
  transform: scale(0.98);
}

.btn-secondary {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-subtle);
}

.btn-secondary:hover {
  border-color: var(--border-hover);
  color: var(--text-primary);
  transform: translateY(-2px);
}

.btn-secondary:active {
  transform: scale(0.98);
}

/* --- Navigation --- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--nav-height);
  transition: background 300ms var(--ease-default), box-shadow 300ms var(--ease-default);
}

.navbar.scrolled {
  background: rgba(10, 10, 15, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 1px 0 var(--border-subtle);
}

.nav-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-family: 'Inter', sans-serif;
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.logo-accent {
  background: var(--gradient-neural);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-link {
  font-size: 15px;
  font-weight: 400;
  color: var(--text-secondary);
  padding: 8px 16px;
  border-radius: 6px;
  transition: color 200ms var(--ease-default);
  position: relative;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 4px;
  left: 50%;
  width: 0;
  height: 2px;
  background: var(--accent-primary);
  transition: width 200ms var(--ease-default), left 200ms var(--ease-default);
}

.nav-link:hover {
  color: var(--text-primary);
}

.nav-link:hover::after {
  width: calc(100% - 32px);
  left: 16px;
}

.nav-link.nav-cta {
  background: var(--cta-primary);
  color: #fff;
  font-weight: 500;
  margin-left: 8px;
}

.nav-link.nav-cta::after {
  display: none;
}

.nav-link.nav-cta:hover {
  background: var(--cta-hover);
  color: #fff;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
  z-index: 1001;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all 300ms var(--ease-default);
}

.nav-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* Mobile Menu */
.mobile-menu {
  position: fixed;
  inset: 0;
  z-index: 999;
  background: rgba(10, 10, 15, 0.98);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: opacity 300ms var(--ease-default), visibility 300ms;
}

.mobile-menu.active {
  opacity: 1;
  visibility: visible;
}

.mobile-nav-links {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.mobile-nav-link {
  font-size: 24px;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 12px 24px;
  transition: color 200ms var(--ease-default);
}

.mobile-nav-link:hover {
  color: var(--text-primary);
}

.mobile-nav-cta {
  margin-top: 16px;
  background: var(--cta-primary);
  color: #fff !important;
  border-radius: 6px;
  font-size: 18px;
}

/* --- Hero --- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
}

.hero-bg canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero-gradient {
  position: absolute;
  inset: 0;
  background: var(--gradient-hero);
  opacity: 0.85;
}

.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: calc(var(--nav-height) + 32px) 24px 80px;
  max-width: 800px;
}

.hero-title {
  font-size: 56px;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 16px;
}

.hero-subtitle {
  font-size: 20px;
  font-weight: 500;
  color: var(--accent-primary);
  margin-bottom: 24px;
}

.hero-desc {
  font-size: 18px;
  line-height: 1.8;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.hero-tagline {
  margin-bottom: 40px;
}

.tagline-en {
  display: block;
  font-family: 'Inter', sans-serif;
  font-size: 16px;
  font-weight: 500;
  letter-spacing: 2px;
  color: var(--text-muted);
  margin-bottom: 8px;
  min-height: 24px;
}

.tagline-kr {
  display: block;
  font-size: 20px;
  font-weight: 700;
  background: var(--gradient-accent);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-cta {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.arrow-down {
  font-size: 18px;
  display: inline-block;
  animation: bounceDown 2s infinite;
}

@keyframes bounceDown {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(4px); }
}

.hero-scroll-indicator {
  position: absolute;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1;
}

.scroll-line {
  width: 1px;
  height: 40px;
  background: var(--border-subtle);
  position: relative;
  overflow: hidden;
}

.scroll-line::after {
  content: '';
  position: absolute;
  top: -40px;
  left: 0;
  width: 100%;
  height: 40px;
  background: var(--accent-primary);
  animation: scrollDown 2s infinite;
}

@keyframes scrollDown {
  0% { top: -40px; }
  100% { top: 40px; }
}

/* --- Sections --- */
.section {
  padding: var(--section-padding) 0;
  position: relative;
}

.section-why {
  background: var(--bg-surface);
}

.section-method {
  background: var(--bg-primary);
}

.section-critical {
  background: var(--bg-surface);
}

.section-diagnosis {
  background: var(--bg-primary);
}

.section-results {
  background: var(--bg-surface);
}

.section-usecases {
  background: var(--bg-primary);
}

.section-philosophy {
  background: var(--bg-surface);
}

.section-contact {
  background: var(--bg-primary);
  padding-bottom: 80px;
}

/* --- Section 2: Why Brain180 --- */
.why-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  margin-bottom: 64px;
}

.why-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 32px 24px;
  transition: border-color 200ms var(--ease-default), transform 200ms var(--ease-default);
}

.why-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.why-card-icon {
  width: 48px;
  height: 48px;
  color: var(--accent-primary);
  margin-bottom: 20px;
}

.why-card-icon svg {
  width: 100%;
  height: 100%;
}

.why-card-title {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.4;
}

.why-card-desc {
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-secondary);
}

.why-bottom {
  text-align: center;
  padding: 40px 24px;
  background: var(--bg-elevated);
  border-radius: 8px;
  border: 1px solid var(--border-subtle);
}

.why-statement {
  font-size: 20px;
  font-weight: 700;
  line-height: 1.6;
  color: var(--accent-primary);
}

/* --- Section 3: Steps --- */
.steps {
  max-width: 640px;
  margin: 0 auto;
  position: relative;
}

.step {
  display: flex;
  gap: 24px;
  position: relative;
  padding-bottom: 48px;
}

.step:last-child {
  padding-bottom: 0;
}

.step:last-child .step-connector .step-line {
  display: none;
}

.step-connector {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  flex-shrink: 0;
  width: 48px;
}

.step-line {
  position: absolute;
  top: 56px;
  left: 50%;
  transform: translateX(-50%);
  width: 2px;
  height: calc(100% - 8px);
  background: var(--border-subtle);
  overflow: hidden;
}

.step-line::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 0%;
  background: var(--gradient-neural);
  transition: height 600ms var(--ease-default);
}

.step.revealed .step-line::after {
  height: 100%;
}

.step-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  position: relative;
  z-index: 1;
  transition: border-color 300ms var(--ease-default), box-shadow 300ms var(--ease-default);
}

.step.revealed .step-number {
  border-color: var(--cta-primary);
  box-shadow: 0 0 20px var(--cta-glow);
}

.step-number span {
  font-family: 'JetBrains Mono', monospace;
  font-size: 16px;
  font-weight: 400;
  color: var(--accent-primary);
}

.step-content {
  padding-top: 8px;
}

.step-title {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 8px;
  line-height: 1.4;
}

.step-desc {
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-secondary);
}

/* --- Section 4: Critical Period Timeline --- */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto 48px;
}

.timeline-track {
  position: absolute;
  top: 20px;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--border-subtle);
  border-radius: 2px;
}

.timeline-progress {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 0%;
  background: var(--gradient-neural);
  border-radius: 2px;
  transition: width 800ms var(--ease-default);
}

.timeline-items {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  padding-top: 48px;
}

.timeline-item {
  text-align: center;
  position: relative;
}

.timeline-dot {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--bg-primary);
  border: 3px solid var(--accent-primary);
  position: absolute;
  top: -36px;
  left: 50%;
  transform: translateX(-50%);
  transition: box-shadow 300ms var(--ease-default);
}

.timeline-item.revealed .timeline-dot {
  box-shadow: 0 0 16px var(--accent-glow);
}

.timeline-age {
  font-family: 'Inter', sans-serif;
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.timeline-badge {
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  font-weight: 400;
  color: var(--cta-primary);
  background: var(--cta-glow);
  display: inline-block;
  padding: 2px 12px;
  border-radius: 4px;
  margin-bottom: 12px;
}

.timeline-label {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 4px;
}

.timeline-sublabel {
  font-size: 14px;
  color: var(--text-muted);
}

.critical-callout {
  text-align: center;
  padding: 32px 24px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
}

.critical-callout p {
  font-size: 20px;
  font-weight: 700;
  line-height: 1.6;
}

/* --- Section 5: Diagnosis --- */
.diag-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
  margin-bottom: 48px;
}

.diag-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 32px 24px;
  position: relative;
  overflow: hidden;
  transition: border-color 200ms var(--ease-default), transform 200ms var(--ease-default);
}

.diag-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.diag-featured {
  grid-column: 1 / -1;
  border-color: var(--border-hover);
  position: relative;
}

.diag-featured::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 8px;
  padding: 1px;
  background: conic-gradient(from 0deg, transparent, var(--cta-primary), transparent, var(--accent-primary), transparent);
  -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  animation: rotateBorder 6s linear infinite;
  opacity: 0;
  transition: opacity 300ms var(--ease-default);
}

.diag-featured:hover::before {
  opacity: 1;
}

@keyframes rotateBorder {
  from { --angle: 0deg; }
  to { --angle: 360deg; }
}

.diag-card-inner {
  position: relative;
  z-index: 1;
}

.diag-number {
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  color: var(--accent-primary);
  margin-bottom: 12px;
}

.diag-title {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 8px;
  line-height: 1.4;
}

.diag-tagline {
  font-size: 14px;
  color: var(--cta-primary);
  font-weight: 500;
  margin-bottom: 12px;
}

.diag-desc {
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-secondary);
}

.diag-cta {
  text-align: center;
}

/* --- Section 6: Results --- */
.results-track {
  position: relative;
  max-width: 900px;
  margin: 0 auto;
}

.results-line {
  position: absolute;
  top: 20px;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--border-subtle);
  border-radius: 2px;
}

.results-line-fill {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 0%;
  background: var(--gradient-neural);
  border-radius: 2px;
  transition: width 800ms var(--ease-default);
}

.results-items {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  padding-top: 48px;
}

.results-item {
  text-align: center;
  position: relative;
}

.results-dot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--bg-surface);
  border: 3px solid var(--accent-primary);
  position: absolute;
  top: -35px;
  left: 50%;
  transform: translateX(-50%);
}

.results-period {
  font-family: 'Inter', sans-serif;
  font-size: 20px;
  font-weight: 700;
  color: var(--accent-primary);
  margin-bottom: 4px;
}

.results-type {
  font-size: 14px;
  font-weight: 500;
  color: var(--cta-primary);
  margin-bottom: 8px;
}

.results-desc {
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-secondary);
}

/* --- Section 7: Use Cases --- */
.usecase-block {
  margin-bottom: 80px;
}

.usecase-block:last-child {
  margin-bottom: 0;
}

.usecase-subtitle {
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 16px;
  line-height: 1.4;
}

.usecase-intro {
  font-size: 18px;
  line-height: 1.8;
  color: var(--text-secondary);
  margin-bottom: 40px;
  max-width: 720px;
}

.competency-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  margin-bottom: 40px;
}

.comp-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 24px;
  text-align: center;
  transition: border-color 200ms var(--ease-default), transform 200ms var(--ease-default);
}

.comp-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.comp-icon {
  font-size: 32px;
  margin-bottom: 12px;
}

.comp-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 8px;
}

.comp-desc {
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-secondary);
}

.usecase-callout {
  padding: 32px 24px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  text-align: center;
  margin-bottom: 40px;
}

.usecase-callout p {
  font-size: 18px;
  font-weight: 500;
  line-height: 1.7;
  color: var(--text-secondary);
}

/* Interview */
.interview-example {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  overflow: hidden;
}

.interview-question {
  padding: 24px 32px;
  border-bottom: 1px solid var(--border-subtle);
}

.interview-label {
  display: block;
  font-family: 'Inter', sans-serif;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--accent-primary);
  margin-bottom: 8px;
}

.interview-question p {
  font-size: 18px;
  font-weight: 700;
  line-height: 1.5;
}

.interview-approach {
  padding: 24px 32px;
}

.approach-steps {
  margin-top: 16px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.approach-step {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.approach-num {
  font-family: 'JetBrains Mono', monospace;
  font-size: 16px;
  color: var(--cta-primary);
  flex-shrink: 0;
  margin-top: 2px;
}

.approach-step strong {
  display: block;
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 4px;
}

.approach-step p {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text-secondary);
}

/* --- Section 8: Philosophy --- */
.philosophy-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
}

.phil-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 40px 32px;
  transition: border-color 200ms var(--ease-default), transform 200ms var(--ease-default);
}

.phil-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.phil-icon {
  width: 48px;
  height: 48px;
  color: var(--accent-primary);
  margin-bottom: 20px;
}

.phil-icon svg {
  width: 100%;
  height: 100%;
}

.phil-keyword {
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 4px;
}

.phil-keyword-en {
  font-family: 'Inter', sans-serif;
  font-size: 14px;
  font-weight: 500;
  color: var(--accent-primary);
  margin-bottom: 16px;
  display: block;
}

.phil-desc {
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-secondary);
}

/* --- Section 9: Contact --- */
.contact-header {
  text-align: center;
  margin-bottom: 64px;
}

.contact-subtitle {
  font-size: 20px;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.contact-body {
  font-size: 18px;
  line-height: 1.8;
  color: var(--text-muted);
}

.contact-form-wrapper {
  max-width: 640px;
  margin: 0 auto;
}

.contact-form {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 40px 32px;
  margin-bottom: 32px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 16px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group.full-width {
  margin-bottom: 16px;
}

.form-group label {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
}

.required {
  color: var(--accent-primary);
}

.form-group input,
.form-group select {
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 12px 16px;
  color: var(--text-primary);
  font-size: 15px;
  outline: none;
  transition: border-color 200ms var(--ease-default);
  -webkit-appearance: none;
  appearance: none;
}

.form-group select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1.5L6 6.5L11 1.5' stroke='%239898B0' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round' fill='none'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 16px center;
  padding-right: 40px;
}

.form-group input:focus,
.form-group select:focus {
  border-color: var(--cta-primary);
}

.form-group input::placeholder {
  color: var(--text-muted);
}

.form-group input.error,
.form-group select.error {
  border-color: #EF4444;
}

.form-error {
  font-size: 12px;
  color: #EF4444;
  min-height: 16px;
}

.btn-submit {
  width: 100%;
  margin-top: 8px;
  padding: 16px;
  font-size: 18px;
  font-weight: 700;
}

.form-success {
  display: none;
  text-align: center;
  padding: 24px;
  margin-top: 16px;
  background: rgba(52, 211, 153, 0.1);
  border: 1px solid var(--success);
  border-radius: 6px;
}

.form-success.visible {
  display: block;
}

.form-success p {
  color: var(--success);
  font-weight: 500;
}

.contact-alt {
  text-align: center;
}

.contact-alt p {
  font-size: 15px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.contact-alt a {
  color: var(--text-secondary);
  transition: color 200ms var(--ease-default);
}

.contact-alt a:hover {
  color: var(--accent-primary);
}

/* --- Footer --- */
.footer {
  background: var(--bg-surface);
  border-top: 1px solid var(--border-subtle);
  padding: 48px 0 32px;
}

.footer-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 32px;
  flex-wrap: wrap;
  gap: 24px;
}

.footer-logo {
  font-family: 'Inter', sans-serif;
  font-size: 20px;
  font-weight: 700;
}

.footer-brand-sub {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 4px;
}

.footer-nav {
  display: flex;
  gap: 32px;
  flex-wrap: wrap;
}

.footer-nav a {
  font-size: 14px;
  color: var(--text-muted);
  transition: color 200ms var(--ease-default);
}

.footer-nav a:hover {
  color: var(--text-primary);
}

.footer-social {
  display: flex;
  gap: 16px;
}

.social-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  color: var(--text-muted);
  transition: color 200ms var(--ease-default), border-color 200ms var(--ease-default);
}

.social-icon:hover {
  color: var(--text-primary);
  border-color: var(--border-hover);
}

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--border-subtle);
  text-align: center;
}

.footer-bottom p {
  font-size: 13px;
  color: var(--text-muted);
}

/* --- Scroll Reveal Animations --- */
.reveal-up {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 600ms var(--ease-out), transform 600ms var(--ease-out);
}

.reveal-up.revealed {
  opacity: 1;
  transform: translateY(0);
}

.delay-1 { transition-delay: 100ms; }
.delay-2 { transition-delay: 200ms; }
.delay-3 { transition-delay: 300ms; }
.delay-4 { transition-delay: 400ms; }

/* --- Reduced Motion --- */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  .reveal-up {
    opacity: 1;
    transform: none;
  }
}

/* --- Responsive --- */

/* Tablet */
@media (max-width: 1024px) {
  :root {
    --section-padding: 96px;
  }

  .section-title {
    font-size: 34px;
  }

  .hero-title {
    font-size: 44px;
  }

  .why-cards {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .competency-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .diag-grid {
    gap: 16px;
  }

  .results-items {
    grid-template-columns: repeat(2, 1fr);
    gap: 40px 24px;
    padding-top: 56px;
  }

  .results-line {
    display: none;
  }

  .results-dot {
    display: none;
  }

  .results-item {
    text-align: left;
  }

  .philosophy-cards {
    grid-template-columns: 1fr;
  }

  .steps {
    max-width: 100%;
  }

  .nav-links {
    display: none;
  }

  .nav-toggle {
    display: flex;
    min-width: 44px;
    min-height: 44px;
    align-items: center;
    justify-content: center;
  }
}

/* Mobile */
@media (max-width: 768px) {
  :root {
    --section-padding: 80px;
    --nav-height: 64px;
  }

  /* Mobile Menu — larger tap targets */
  .mobile-nav-link {
    font-size: 22px;
    padding: 14px 24px;
    min-height: 48px;
    display: flex;
    align-items: center;
  }

  /* Hero — mobile */
  .hero-title {
    font-size: 32px;
  }

  .hero-title br {
    display: none;
  }

  .hero-desc br {
    display: none;
  }

  .hero-subtitle {
    font-size: 18px;
  }

  .hero-desc {
    font-size: 16px;
  }

  .tagline-en {
    font-size: 13px;
    letter-spacing: 1px;
  }

  .tagline-kr {
    font-size: 17px;
  }

  .hero-tagline {
    margin-bottom: 32px;
  }

  .hero-cta {
    flex-direction: column;
    align-items: center;
  }

  .hero-cta .btn {
    width: 100%;
    max-width: 320px;
    white-space: normal;
    text-align: center;
  }

  .hero-scroll-indicator {
    bottom: 16px;
  }

  /* Section titles — mobile */
  .section-title {
    font-size: 28px;
  }

  .section-title br {
    display: none;
  }

  .section-intro {
    font-size: 16px;
    margin-bottom: 40px;
  }

  .section-intro br {
    display: none;
  }

  /* Why section — mobile */
  .why-statement {
    font-size: 17px;
  }

  .why-statement br {
    display: none;
  }

  .why-bottom {
    padding: 28px 20px;
  }

  /* Steps — mobile */
  .step {
    gap: 16px;
  }

  .step-title {
    font-size: 20px;
  }

  .step-number {
    width: 40px;
    height: 40px;
  }

  .step-number span {
    font-size: 14px;
  }

  .step-line {
    top: 48px;
  }

  /* Timeline — mobile (vertical layout) */
  .timeline-items {
    grid-template-columns: 1fr;
    gap: 32px;
    padding-top: 24px;
  }

  .timeline-track {
    display: none;
  }

  .timeline-dot {
    display: none;
  }

  .timeline-item {
    text-align: left;
    padding-left: 24px;
    border-left: 2px solid var(--border-subtle);
  }

  .timeline-age {
    font-size: 16px;
  }

  .timeline-label {
    font-size: 16px;
  }

  /* Diagnosis — mobile */
  .diag-grid {
    grid-template-columns: 1fr;
  }

  .diag-featured {
    grid-column: auto;
  }

  .diag-card {
    padding: 24px 20px;
  }

  .diag-title {
    font-size: 20px;
  }

  /* Results — mobile (vertical, no line) */
  .results-items {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .results-item {
    text-align: left;
    padding-left: 24px;
    border-left: 2px solid var(--border-subtle);
  }

  .results-dot {
    display: none;
  }

  .results-period {
    font-size: 18px;
  }

  /* Use Cases — mobile */
  .competency-grid {
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }

  .comp-card {
    padding: 16px;
  }

  .comp-icon {
    font-size: 24px;
    margin-bottom: 8px;
  }

  .comp-title {
    font-size: 15px;
  }

  .comp-desc {
    font-size: 13px;
  }

  .usecase-subtitle {
    font-size: 24px;
  }

  .usecase-intro {
    font-size: 16px;
    margin-bottom: 28px;
  }

  .usecase-callout p {
    font-size: 16px;
  }

  /* Interview — mobile */
  .interview-question,
  .interview-approach {
    padding: 20px;
  }

  .interview-question p {
    font-size: 16px;
  }

  .approach-step {
    gap: 12px;
  }

  .approach-step strong {
    font-size: 15px;
  }

  .approach-step p {
    font-size: 14px;
  }

  /* Philosophy — mobile */
  .philosophy-cards {
    grid-template-columns: 1fr;
  }

  .phil-card {
    padding: 32px 24px;
  }

  .phil-keyword {
    font-size: 24px;
  }

  /* Contact — mobile */
  .contact-subtitle {
    font-size: 17px;
  }

  .contact-body {
    font-size: 16px;
  }

  .contact-form {
    padding: 24px 20px;
  }

  .form-row {
    grid-template-columns: 1fr;
  }

  .btn-submit {
    font-size: 16px;
    padding: 14px;
  }

  /* Callouts — mobile */
  .critical-callout {
    padding: 24px 20px;
  }

  .critical-callout p,
  .why-bottom p {
    font-size: 17px;
  }

  .critical-callout p br {
    display: none;
  }

  /* Footer — mobile */
  .footer-top {
    flex-direction: column;
    align-items: flex-start;
    gap: 24px;
  }

  .footer-nav {
    gap: 16px;
    flex-wrap: wrap;
  }

  .footer-nav a {
    min-height: 44px;
    display: flex;
    align-items: center;
  }
}

/* Small mobile (iPhone SE, etc.) */
@media (max-width: 375px) {
  .hero-title {
    font-size: 26px;
  }

  .hero-subtitle {
    font-size: 16px;
  }

  .hero-desc {
    font-size: 15px;
  }

  .tagline-kr {
    font-size: 15px;
  }

  .container {
    padding: 0 16px;
  }

  .section-title {
    font-size: 24px;
  }

  .competency-grid {
    grid-template-columns: 1fr;
  }

  .comp-card {
    padding: 20px;
  }

  .comp-title {
    font-size: 16px;
  }

  .comp-desc {
    font-size: 14px;
  }

  .phil-keyword {
    font-size: 22px;
  }

  .diag-title {
    font-size: 18px;
  }

  .why-card-title {
    font-size: 20px;
  }

  .why-card {
    padding: 24px 20px;
  }
}