/* ============================================================
   IINA 官方网站 - 主样式表
   配色基于 IINA Logo: 深邃渐变 + 亮蓝青色 (#00B0F0 / #00D2FC)
   设计风格: 扁平现代专业
   ============================================================ */

/* ---------- CSS Variables ---------- */
:root {
  /* Brand colors extracted from logo */
  --color-bg-dark: #0A0A1A;
  --color-bg-darker: #06060F;
  --color-bg-card-dark: #15152A;
  --color-purple-deep: #1F2350;
  --color-purple: #252983;
  --color-primary: #00B0F0;
  --color-primary-dark: #0090D0;
  --color-primary-light: #00D2FC;
  --color-accent-cyan: #00E5FF;

  /* Light theme surfaces */
  --color-bg-white: #FFFFFF;
  --color-bg-soft: #F7F8FC;
  --color-bg-soft-alt: #F0F2F8;

  /* Text */
  --color-text-dark: #1A1A2E;
  --color-text-body: #2D2D44;
  --color-text-muted: #6B6B85;
  --color-text-light: #FFFFFF;
  --color-text-light-muted: #B8B8CC;

  /* Borders & dividers */
  --color-border: #E5E7EB;
  --color-border-dark: rgba(255,255,255,0.08);

  /* Gradients */
  --gradient-hero: linear-gradient(135deg, #06060F 0%, #1F2350 40%, #252983 70%, #0090D0 100%);
  --gradient-accent: linear-gradient(135deg, #00B0F0 0%, #00D2FC 100%);
  --gradient-accent-hover: linear-gradient(135deg, #0090D0 0%, #00B0F0 100%);
  --gradient-card: linear-gradient(180deg, #FFFFFF 0%, #F7F8FC 100%);
  --gradient-card-dark: linear-gradient(180deg, #15152A 0%, #0A0A1A 100%);

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "PingFang SC", "Helvetica Neue", "Microsoft YaHei", sans-serif;
  --font-mono: "SF Mono", "JetBrains Mono", "Fira Code", Consolas, monospace;

  /* Spacing scale */
  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(15,15,30,0.06);
  --shadow-md: 0 4px 16px rgba(15,15,30,0.08);
  --shadow-lg: 0 12px 32px rgba(15,15,30,0.12);
  --shadow-xl: 0 24px 60px rgba(15,15,30,0.16);
  --shadow-glow: 0 8px 32px rgba(0,176,240,0.25);

  /* Layout */
  --container-max: 1200px;
  --header-height: 64px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--color-text-body);
  background: var(--color-bg-white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

a {
  color: var(--color-primary-dark);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary);
}

ul, ol {
  list-style: none;
}

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

/* ---------- Typography ---------- */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-dark);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h1 {
  font-size: clamp(2.25rem, 5vw, 3.75rem);
  font-weight: 800;
}

h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
}

h3 {
  font-size: clamp(1.25rem, 2vw, 1.5rem);
}

h4 {
  font-size: 1.125rem;
}

p {
  margin-bottom: 1rem;
}

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

.text-light {
  color: var(--color-text-light);
}

.text-light-muted {
  color: var(--color-text-light-muted);
}

/* ---------- Layout utilities ---------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.section {
  padding: var(--space-4xl) 0;
}

.section-sm {
  padding: var(--space-3xl) 0;
}

.section-dark {
  background: var(--color-bg-dark);
  color: var(--color-text-light-muted);
}

.section-dark h1,
.section-dark h2,
.section-dark h3,
.section-dark h4 {
  color: var(--color-text-light);
}

.section-soft {
  background: var(--color-bg-soft);
}

.section-header {
  text-align: center;
  max-width: 720px;
  margin: 0 auto var(--space-3xl);
}

.section-header .eyebrow {
  display: inline-block;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-primary-dark);
  padding: 0.375rem 0.875rem;
  background: rgba(0,176,240,0.08);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-md);
}

.section-dark .section-header .eyebrow {
  color: var(--color-primary-light);
  background: rgba(0,210,252,0.1);
}

.section-header h2 {
  margin-bottom: var(--space-md);
}

.section-header p {
  font-size: 1.0625rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
}

.section-dark .section-header p {
  color: var(--color-text-light-muted);
}

/* ---------- Header / Navigation ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.85);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  font-weight: 700;
  font-size: 1.1875rem;
  color: var(--color-text-dark);
  letter-spacing: -0.01em;
}

.brand img {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
}

.brand:hover {
  color: var(--color-text-dark);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.main-nav a {
  color: var(--color-text-body);
  font-size: 0.9375rem;
  font-weight: 500;
  padding: 0.5rem 0;
  position: relative;
  transition: color var(--transition-fast);
}

.main-nav a:hover {
  color: var(--color-primary-dark);
}

.main-nav a.active {
  color: var(--color-primary-dark);
}

.main-nav a.active::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  bottom: -4px;
  height: 2px;
  background: var(--gradient-accent);
  border-radius: 1px;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
  cursor: pointer;
  white-space: nowrap;
  border: 1px solid transparent;
}

.btn-primary {
  background: var(--gradient-accent);
  color: var(--color-text-light);
  box-shadow: var(--shadow-glow);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 12px 40px rgba(0,176,240,0.4);
  color: var(--color-text-light);
}

.btn-secondary {
  background: var(--color-text-dark);
  color: var(--color-text-light);
}

.btn-secondary:hover {
  background: #2D2D44;
  color: var(--color-text-light);
}

.btn-outline {
  background: transparent;
  border-color: var(--color-border);
  color: var(--color-text-dark);
}

.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary-dark);
  background: rgba(0,176,240,0.04);
}

.btn-ghost-light {
  background: rgba(255,255,255,0.08);
  color: var(--color-text-light);
  border-color: rgba(255,255,255,0.15);
}

.btn-ghost-light:hover {
  background: rgba(255,255,255,0.15);
  color: var(--color-text-light);
}

.btn-lg {
  padding: 0.9375rem 2rem;
  font-size: 1rem;
}

.btn-sm {
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  background: var(--gradient-hero);
  color: var(--color-text-light);
  padding: var(--space-4xl) 0 var(--space-3xl);
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -10%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(0,210,252,0.18) 0%, transparent 60%);
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -30%;
  left: -10%;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, rgba(37,41,131,0.5) 0%, transparent 60%);
  pointer-events: none;
}

.hero .container {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: var(--space-3xl);
  align-items: center;
}

.hero-content {
  max-width: 560px;
}

.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.375rem 0.875rem;
  background: rgba(255,255,255,0.1);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-light-muted);
  margin-bottom: var(--space-lg);
}

.hero-eyebrow .dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-primary-light);
  box-shadow: 0 0 8px var(--color-primary-light);
}

.hero h1 {
  color: var(--color-text-light);
  margin-bottom: var(--space-lg);
  letter-spacing: -0.03em;
}

.hero-subtitle {
  font-size: 1.1875rem;
  color: var(--color-text-light-muted);
  margin-bottom: var(--space-2xl);
  line-height: 1.6;
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  margin-bottom: var(--space-2xl);
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xl);
  font-size: 0.875rem;
  color: var(--color-text-light-muted);
}

.hero-meta-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.hero-meta-item strong {
  color: var(--color-text-light);
  font-weight: 600;
}

.hero-visual {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-logo-wrap {
  position: relative;
  width: 100%;
  max-width: 420px;
  aspect-ratio: 1;
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-logo-wrap::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at center, rgba(0,176,240,0.25), transparent 70%);
  filter: blur(40px);
}

.hero-logo {
  position: relative;
  width: 75%;
  border-radius: var(--radius-xl);
  box-shadow: 0 30px 80px rgba(0,0,0,0.5);
  z-index: 1;
}

.hero-logo-glow {
  position: absolute;
  inset: -20px;
  border-radius: var(--radius-xl);
  background: linear-gradient(135deg, rgba(0,176,240,0.4), rgba(0,210,252,0.2));
  filter: blur(30px);
  z-index: 0;
}

/* ---------- Feature Grid ---------- */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
}

.feature-card {
  background: var(--color-bg-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.feature-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--gradient-accent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-base);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(0,176,240,0.3);
}

.feature-card:hover::before {
  transform: scaleX(1);
}

.feature-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, rgba(0,176,240,0.12), rgba(0,210,252,0.08));
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
  color: var(--color-primary-dark);
}

.feature-icon svg {
  width: 24px;
  height: 24px;
}

.feature-card h3 {
  margin-bottom: var(--space-sm);
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 0;
}

/* Dark section variant */
.section-dark .feature-card {
  background: var(--color-bg-card-dark);
  border-color: var(--color-border-dark);
}

.section-dark .feature-card h3 {
  color: var(--color-text-light);
}

.section-dark .feature-card p {
  color: var(--color-text-light-muted);
}

.section-dark .feature-icon {
  background: linear-gradient(135deg, rgba(0,176,240,0.18), rgba(0,210,252,0.12));
  color: var(--color-primary-light);
}

/* ---------- Scenario Section ---------- */
.scenario-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-lg);
}

.scenario-card {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--gradient-card);
  border: 1px solid var(--color-border);
  padding: var(--space-xl);
  transition: all var(--transition-base);
}

.scenario-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.scenario-number {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-primary-dark);
  letter-spacing: 0.1em;
  margin-bottom: var(--space-md);
}

.scenario-card h3 {
  margin-bottom: var(--space-sm);
}

.scenario-card p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 0;
}

/* ---------- Testimonials ---------- */
.testimonial-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-lg);
}

.testimonial-card {
  background: var(--color-bg-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  position: relative;
  transition: all var(--transition-base);
}

.testimonial-card:hover {
  box-shadow: var(--shadow-md);
}

.testimonial-quote-mark {
  font-family: Georgia, serif;
  font-size: 3rem;
  line-height: 1;
  color: var(--color-primary);
  opacity: 0.25;
  margin-bottom: var(--space-sm);
}

.testimonial-text {
  font-size: 1rem;
  line-height: 1.65;
  color: var(--color-text-body);
  margin-bottom: var(--space-lg);
}

.testimonial-author {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.testimonial-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--gradient-accent);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-light);
  font-weight: 600;
  font-size: 0.9375rem;
  flex-shrink: 0;
}

.testimonial-author-info {
  flex: 1;
}

.testimonial-author-name {
  font-weight: 600;
  color: var(--color-text-dark);
  font-size: 0.9375rem;
}

.testimonial-author-meta {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

/* ---------- Stats ---------- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-xl);
  text-align: center;
}

.stat-value {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 800;
  background: var(--gradient-accent);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.02em;
  line-height: 1.1;
  margin-bottom: var(--space-xs);
}

.section-dark .stat-value {
  background: linear-gradient(135deg, #00D2FC 0%, #FFFFFF 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.stat-label {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

.section-dark .stat-label {
  color: var(--color-text-light-muted);
}

/* ---------- CTA Section ---------- */
.cta-section {
  background: var(--gradient-hero);
  position: relative;
  overflow: hidden;
  text-align: center;
  padding: var(--space-4xl) 0;
}

.cta-section::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, rgba(0,176,240,0.15) 0%, transparent 60%);
  pointer-events: none;
}

.cta-section .container {
  position: relative;
  z-index: 1;
  max-width: 720px;
}

.cta-section h2 {
  color: var(--color-text-light);
  margin-bottom: var(--space-md);
}

.cta-section p {
  color: var(--color-text-light-muted);
  font-size: 1.125rem;
  margin-bottom: var(--space-2xl);
}

.cta-section .hero-cta {
  justify-content: center;
}

/* ---------- Detail Content (features page) ---------- */
.detail-section {
  padding: var(--space-3xl) 0;
  border-bottom: 1px solid var(--color-border);
}

.detail-section:last-child {
  border-bottom: none;
}

.detail-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-3xl);
  align-items: center;
}

.detail-row.reverse {
  direction: rtl;
}

.detail-row.reverse > * {
  direction: ltr;
}

.detail-content h3 {
  font-size: 1.75rem;
  margin-bottom: var(--space-md);
}

.detail-content .detail-eyebrow {
  display: inline-block;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-primary-dark);
  margin-bottom: var(--space-sm);
}

.detail-content p {
  color: var(--color-text-muted);
  font-size: 1rem;
  margin-bottom: var(--space-md);
}

.detail-list {
  margin-top: var(--space-lg);
}

.detail-list li {
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
  color: var(--color-text-body);
  font-size: 0.9375rem;
}

.detail-list li::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-primary);
  margin-top: 0.5rem;
  flex-shrink: 0;
}

.detail-visual {
  background: var(--gradient-card-dark);
  border-radius: var(--radius-xl);
  padding: var(--space-2xl);
  min-height: 320px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-border-dark);
  position: relative;
  overflow: hidden;
}

.detail-visual-icon {
  width: 120px;
  height: 120px;
  color: var(--color-primary-light);
  opacity: 0.9;
}

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

/* ---------- Download Page ---------- */
.download-options {
  display: grid;
  max-width: 580px;
  margin:0 auto;
  gap: var(--space-lg);
  margin-bottom: var(--space-3xl);
}

.download-card {
  background: var(--color-bg-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-2xl);
  text-align: center;
  transition: all var(--transition-base);
  position: relative;
}

.download-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(0,176,240,0.3);
}

.download-card.recommended {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-glow);
}

.download-card .badge {
  position: absolute;
  top: -10px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--gradient-accent);
  color: var(--color-text-light);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.25rem 0.875rem;
  border-radius: var(--radius-full);
  letter-spacing: 0.04em;
}

.download-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto var(--space-lg);
  color: var(--color-primary-dark);
  background: linear-gradient(135deg, rgba(0,176,240,0.12), rgba(0,210,252,0.08));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
}

.download-icon svg {
  width: 32px;
  height: 32px;
}

.download-card h3 {
  margin-bottom: var(--space-xs);
}

.download-card .version {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin-bottom: var(--space-lg);
}

.download-card .file-info {
  background: var(--color-bg-soft);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-bottom: var(--space-lg);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  text-align: left;
}

.download-card .file-info div {
  display: flex;
  justify-content: space-between;
  padding: 0.25rem 0;
}

.download-card .file-info strong {
  color: var(--color-text-body);
  font-weight: 500;
}

/* ---------- Version History ---------- */
.version-list {
  max-width: 800px;
  margin: 0 auto;
}

.version-item {
  display: grid;
  grid-template-columns: 140px 1fr;
  gap: var(--space-xl);
  padding: var(--space-lg) 0;
  border-bottom: 1px solid var(--color-border);
}

.version-item:last-child {
  border-bottom: none;
}

.version-number {
  font-family: var(--font-mono);
  font-weight: 600;
  color: var(--color-primary-dark);
}

.version-date {
  display: block;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  font-weight: 400;
  margin-top: 0.25rem;
}

.version-changes li {
  position: relative;
  padding-left: var(--space-lg);
  margin-bottom: 0.5rem;
  font-size: 0.9375rem;
  color: var(--color-text-body);
}

.version-changes li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.625rem;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--color-primary);
}

/* ---------- FAQ ---------- */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-md);
  overflow: hidden;
  transition: all var(--transition-base);
}

.faq-item[open] {
  border-color: rgba(0,176,240,0.3);
  box-shadow: var(--shadow-sm);
}

.faq-item summary {
  padding: var(--space-md) var(--space-lg);
  font-weight: 600;
  color: var(--color-text-dark);
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 1rem;
}

.faq-item summary::-webkit-details-marker {
  display: none;
}

.faq-item summary::after {
  content: '+';
  font-size: 1.5rem;
  font-weight: 300;
  color: var(--color-primary-dark);
  transition: transform var(--transition-base);
}

.faq-item[open] summary::after {
  transform: rotate(45deg);
}

.faq-answer {
  padding: 0 var(--space-lg) var(--space-lg);
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  line-height: 1.7;
}

/* ---------- About Page ---------- */
.story-block {
  max-width: 760px;
  margin: 0 auto;
}

.story-block p {
  font-size: 1.0625rem;
  color: var(--color-text-body);
  margin-bottom: var(--space-lg);
  line-height: 1.75;
}

.value-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-lg);
}

.value-card {
  text-align: center;
  padding: var(--space-xl);
}

.value-card .value-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto var(--space-md);
  background: linear-gradient(135deg, rgba(0,176,240,0.12), rgba(0,210,252,0.08));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary-dark);
}

.value-card h4 {
  margin-bottom: var(--space-xs);
}

.value-card p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 0;
}

/* ---------- Tech Stack ---------- */
.tech-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: var(--space-md);
}

.tech-item {
  background: var(--color-bg-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  text-align: center;
  transition: all var(--transition-base);
}

.tech-item:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

.tech-item .tech-name {
  font-weight: 600;
  color: var(--color-text-dark);
  margin-bottom: 0.25rem;
}

.tech-item .tech-desc {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

/* ---------- Footer ---------- */
.site-footer {
  background: var(--color-bg-darker);
  color: var(--color-text-light-muted);
  padding: var(--space-3xl) 0 var(--space-xl);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr repeat(3, 1fr);
  gap: var(--space-2xl);
  margin-bottom: var(--space-2xl);
  padding-bottom: var(--space-2xl);
  border-bottom: 1px solid var(--color-border-dark);
}

.footer-brand .brand {
  color: var(--color-text-light);
  margin-bottom: var(--space-md);
}

.footer-brand p {
  font-size: 0.875rem;
  line-height: 1.65;
  color: var(--color-text-light-muted);
  max-width: 320px;
}

.footer-col h5 {
  color: var(--color-text-light);
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-bottom: var(--space-md);
}

.footer-col ul li {
  margin-bottom: var(--space-sm);
}

.footer-col a {
  color: var(--color-text-light-muted);
  font-size: 0.875rem;
  transition: color var(--transition-fast);
}

.footer-col a:hover {
  color: var(--color-primary-light);
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-md);
  font-size: 0.8125rem;
}

.footer-bottom a {
  color: var(--color-text-light-muted);
}

.footer-bottom a:hover {
  color: var(--color-primary-light);
}

/* ---------- Modal (Download Popup) ---------- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(10,10,26,0.75);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: var(--space-lg);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.modal-overlay.active {
  display: flex;
  opacity: 1;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
}
button { outline: none } 
.modal {
  background: var(--color-bg-white);
  border-radius: var(--radius-xl);
  max-width: 720px;
  width: 100%;
  max-height: 90vh;
  overflow-y: auto;
  position: relative;
  transform: translateY(20px) scale(0.96);
  transition: transform var(--transition-base);
  box-shadow: var(--shadow-xl);
}

.modal-overlay.active .modal {
  transform: translateY(0) scale(1);
}

.modal-header {
  padding: var(--space-2xl) var(--space-2xl) var(--space-lg);
  text-align: center;
  border-bottom: 1px solid var(--color-border);
  position: relative;
}

.modal-close {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--color-bg-soft);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-size: 1.25rem;
  transition: all var(--transition-fast);
}

.modal-close:hover {
  background: var(--color-border);
  color: var(--color-text-dark);
}

.modal-header h3 {
  font-size: 1.5rem;
  margin-bottom: var(--space-xs);
}

.modal-header p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  margin-bottom: 0;
}

.modal-body {
  padding: var(--space-2xl);
}

.qr-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
}

.qr-item {
  text-align: center;
  padding: var(--space-lg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: all var(--transition-base);
}

.qr-item:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

.qr-item img {
  width: 180px;
  height: 180px;
  margin: 0 auto var(--space-md);
  border-radius: var(--radius-md);
  background: white;
  padding: 8px;
}

.qr-item h4 {
  margin-bottom: 0.25rem;
  color: var(--color-text-dark);
}

.qr-item p {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
}

.modal-footer {
  padding: var(--space-lg) var(--space-2xl) var(--space-2xl);
  text-align: center;
  border-top: 1px solid var(--color-border);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

/* ---------- Page Hero (inner pages) ---------- */
.page-hero {
  background: var(--gradient-hero);
  color: var(--color-text-light);
  padding: var(--space-3xl) 0;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.page-hero::before {
  content: '';
  position: absolute;
  top: -30%;
  right: -10%;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, rgba(0,210,252,0.15) 0%, transparent 60%);
  pointer-events: none;
}

.page-hero .container {
  position: relative;
  z-index: 1;
  max-width: 760px;
}

.page-hero h1 {
  color: var(--color-text-light);
  margin-bottom: var(--space-md);
}

.page-hero p {
  font-size: 1.125rem;
  color: var(--color-text-light-muted);
  margin-bottom: 0;
}

.breadcrumb {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  color: var(--color-text-light-muted);
  margin-bottom: var(--space-lg);
}

.breadcrumb a {
  color: var(--color-text-light-muted);
}

.breadcrumb a:hover {
  color: var(--color-text-light);
}

.breadcrumb-sep {
  opacity: 0.5;
}

/* ---------- Mobile Menu Toggle ---------- */
.menu-toggle {
  display: none;
  width: 40px;
  height: 40px;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
}

.menu-toggle span {
  width: 20px;
  height: 2px;
  background: var(--color-text-dark);
  border-radius: 1px;
  transition: all var(--transition-base);
}

.menu-toggle.active span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

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

.menu-toggle.active span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ---------- Animations ---------- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in-up {
  animation: fadeInUp 0.6s cubic-bezier(0.16, 1, 0.3, 1) both;
}

/* ---------- Responsive ---------- */
@media (max-width: 968px) {
  .hero .container {
    grid-template-columns: 1fr;
    gap: var(--space-2xl);
  }

  .hero-visual {
    order: -1;
  }

  .hero-logo-wrap {
    max-width: 280px;
  }

  .detail-row,
  .detail-row.reverse {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
  }

  .footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  .container {
    padding: 0 var(--space-md);
  }

  .menu-toggle {
    display: flex;
  }

  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--color-bg-white);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-lg);
    gap: var(--space-md);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition-base);
  }

  .main-nav.active {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .main-nav .btn {
    width: 100%;
  }

  .section {
    padding: var(--space-3xl) 0;
  }

  .hero {
    padding: var(--space-3xl) 0;
  }

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

  .hero-cta .btn {
    width: 100%;
  }

  .hero-meta {
    flex-direction: column;
    gap: var(--space-sm);
  }

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

  .version-item {
    grid-template-columns: 1fr;
    gap: var(--space-sm);
  }

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

  .footer-bottom {
    flex-direction: column;
    text-align: center;
  }

  .modal-body {
    padding: var(--space-lg);
  }

  .modal-header {
    padding: var(--space-xl) var(--space-lg) var(--space-md);
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.5rem;
  }

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

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

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 3px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}