:root {
  --bg: #f4f7fc;
  --surface: #ffffff;
  --surface-muted: #f8faff;
  --text: #1e293b;
  --muted: #475569;
  --line: #dbe4f0;
  --primary: #2563eb;
  --secondary: #3b82f6;
  --radius-xl: 20px;
  --radius-lg: 14px;
  --shadow-sm: 0 10px 24px rgba(15, 23, 42, 0.08);
  --shadow-md: 0 16px 34px rgba(15, 23, 42, 0.11);
  --focus-ring: 0 0 0 3px rgba(37, 99, 235, 0.24);
  --header-bg: rgba(244, 247, 252, 0.86);
}

[data-theme="dark"] {
  --bg: #0b1322;
  --surface: #101a2f;
  --surface-muted: #172541;
  --text: #e2e8f0;
  --muted: #9fb1cc;
  --line: #283b5c;
  --primary: #60a5fa;
  --secondary: #3b82f6;
  --shadow-sm: 0 12px 26px rgba(2, 8, 23, 0.55);
  --shadow-md: 0 18px 36px rgba(2, 8, 23, 0.64);
  --focus-ring: 0 0 0 3px rgba(96, 165, 250, 0.34);
  --header-bg: rgba(11, 19, 34, 0.88);
}

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

body {
  font-family: "Open Sans", "Noto Sans", "Segoe UI", sans-serif;
  color: var(--text);
  line-height: 1.6;
  background:
    radial-gradient(circle at 8% 12%, rgba(37, 99, 235, 0.11), transparent 40%),
    radial-gradient(circle at 92% 5%, rgba(59, 130, 246, 0.09), transparent 36%),
    linear-gradient(180deg, var(--bg) 0%, #f9fbff 100%);
}

[data-theme="dark"] body,
[data-theme="dark"] {
  background:
    radial-gradient(circle at 8% 12%, rgba(96, 165, 250, 0.17), transparent 42%),
    radial-gradient(circle at 92% 5%, rgba(59, 130, 246, 0.13), transparent 36%),
    linear-gradient(180deg, var(--bg) 0%, #0f1a30 100%);
}

.container {
  width: min(1100px, calc(100% - 40px));
  margin: 0 auto;
}

.header {
  position: sticky;
  top: 10px;
  z-index: 20;
  margin-top: 10px;
  padding: 10px 0;
  background: var(--header-bg);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.header-controls {
  display: flex;
  align-items: center;
  gap: 8px;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  color: var(--muted);
  font-weight: 700;
  font-size: 0.86rem;
  padding: 6px 8px;
  border-radius: 10px;
  transition: color 180ms ease, background-color 180ms ease;
}

.back-link svg {
  width: 18px;
  height: 18px;
  fill: currentColor;
}

.back-link:hover {
  color: var(--primary);
  background: rgba(37, 99, 235, 0.08);
}

.theme-toggle,
.lang-toggle {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--surface);
  color: var(--text);
  height: 34px;
  padding: 0 12px;
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
  transition: border-color 180ms ease, color 180ms ease, box-shadow 180ms ease, transform 180ms ease;
}

.theme-toggle {
  width: 38px;
  padding: 0;
}

.theme-toggle:hover,
.lang-toggle:hover {
  border-color: var(--primary);
  color: var(--primary);
  box-shadow: 0 10px 18px rgba(37, 99, 235, 0.14);
  transform: translateY(-1px);
}

.lang-toggle .active {
  color: var(--primary);
}

.hero {
  padding: 42px 0 26px;
  text-align: center;
}

.example-badge {
  display: inline-block;
  border: 1px solid #bfdbfe;
  border-radius: 999px;
  background: #eff6ff;
  color: #1d4ed8;
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.05em;
  padding: 6px 12px;
  margin-bottom: 14px;
}

[data-theme="dark"] .example-badge {
  border-color: #36527f;
  background: #132746;
  color: #93c5fd;
}

.hero h1 {
  font-size: clamp(1.85rem, 4.2vw, 2.7rem);
  line-height: 1.1;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
  color: var(--text);
}

.hero-desc {
  color: var(--muted);
  font-size: clamp(0.97rem, 1.8vw, 1.1rem);
  max-width: 70ch;
  margin: 0 auto;
}

.section {
  padding: 34px 0;
}

.section-title {
  font-size: 1.36rem;
  font-weight: 700;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.section-title::before {
  content: "";
  width: 4px;
  height: 22px;
  border-radius: 4px;
  background: linear-gradient(180deg, var(--primary) 0%, var(--secondary) 100%);
}

.task-card,
.workflow,
.gallery-item,
.video-item,
.nav-link {
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
}

.task-card,
.workflow {
  padding: 16px;
}

.task-label {
  font-size: 0.73rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 800;
  color: var(--primary);
  margin-bottom: 8px;
}

.task-text {
  font-size: 0.96rem;
  color: var(--text);
  line-height: 1.7;
}

.workflow-img {
  width: 100%;
  display: block;
  border-radius: 10px;
  border: 1px solid var(--line);
  cursor: zoom-in;
}

.workflow-caption {
  margin-top: 10px;
  color: var(--muted);
  font-size: 0.85rem;
  text-align: center;
}

.gallery,
.video-gallery {
  display: grid;
  gap: 16px;
}

.gallery-2col,
.video-gallery {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.gallery-item,
.video-item {
  overflow: hidden;
}

.gallery-item img,
.video-item img {
  width: 100%;
  display: block;
  cursor: zoom-in;
  transition: transform 220ms ease;
  border-bottom: 1px solid var(--line);
}

.gallery-item:hover img,
.video-item:hover img {
  transform: scale(1.015);
}

.gallery-caption,
.video-caption {
  padding: 14px 16px;
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.6;
}

.gallery-caption strong,
.video-caption strong {
  color: var(--text);
  font-weight: 700;
}

.lightbox {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 1000;
  background: rgba(2, 8, 23, 0.94);
  padding: 36px;
  justify-content: center;
  align-items: center;
}

.lightbox.active {
  display: flex;
}

.lightbox img {
  max-width: 100%;
  max-height: 100%;
  border-radius: 10px;
}

.lightbox-close {
  position: absolute;
  top: 16px;
  right: 18px;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid rgba(255, 255, 255, 0.36);
  background: rgba(15, 23, 42, 0.45);
  color: #fff;
  font-size: 1.6rem;
  line-height: 1;
  cursor: pointer;
}

.nav-section {
  padding: 36px 0 56px;
}

.nav-links {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.nav-link {
  text-decoration: none;
  padding: 14px 16px;
  transition: border-color 180ms ease, transform 180ms ease, box-shadow 180ms ease;
}

.nav-link:hover {
  border-color: #9fc0ef;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.nav-link-label {
  font-size: 0.73rem;
  color: var(--muted);
  margin-bottom: 4px;
}

.nav-link-title {
  font-size: 0.94rem;
  font-weight: 700;
  color: var(--text);
}

.nav-link.next {
  text-align: right;
}

.theme-toggle:focus-visible,
.lang-toggle:focus-visible,
.back-link:focus-visible,
.nav-link:focus-visible,
.gallery-item img:focus-visible,
.video-item img:focus-visible,
.workflow-img:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

@media (max-width: 900px) {
  .gallery-2col,
  .video-gallery,
  .nav-links {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .container {
    width: min(1100px, calc(100% - 26px));
  }

  .header {
    top: 6px;
    margin-top: 6px;
    padding: 8px 0;
  }

  .hero {
    padding: 30px 0 20px;
  }

  .task-card,
  .workflow {
    padding: 12px;
  }

  .section {
    padding: 28px 0;
  }

  .lightbox {
    padding: 18px;
  }
}