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

:root {
  --brand: #2563eb;
  --brand-dark: #1d4ed8;
  --text: #1e293b;
  --muted: #64748b;
  --border: #e2e8f0;
  --bg: #f8fafc;
  --white: #ffffff;
  --radius: 8px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}

/* ── Header ── */
header {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
}

.header-inner {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  height: 64px;
  gap: 12px;
}

.site-logo {
  height: 36px;
  width: auto;
  display: block;
}

.site-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--brand);
  text-decoration: none;
}

.header-spacer { flex: 1; }

.btn-signin {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  background: var(--brand);
  color: #fff;
  font-size: 0.875rem;
  font-weight: 600;
  border-radius: var(--radius);
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.15s;
}

.btn-signin:hover { background: var(--brand-dark); }

/* ── Breadcrumb ── */
.breadcrumb {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
}

.breadcrumb-inner {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 8px;
  height: 40px;
  font-size: 0.85rem;
  color: var(--muted);
}

.breadcrumb a {
  color: var(--brand);
  text-decoration: none;
}

.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { color: var(--muted); }

/* ── Main layout ── */
main {
  max-width: 900px;
  margin: 40px auto;
  padding: 0 24px;
}

/* ── Home hero ── */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}

.hero h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.hero p {
  color: var(--muted);
  font-size: 1.05rem;
}

/* ── Collection cards ── */
.collections {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
  margin-top: 40px;
}

.card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-decoration: none;
  color: var(--text);
  transition: box-shadow 0.15s, border-color 0.15s;
  display: block;
}

.card:hover {
  border-color: var(--brand);
  box-shadow: 0 4px 12px rgba(37,99,235,0.1);
}

.card h2 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--brand);
}

.card p {
  font-size: 0.9rem;
  color: var(--muted);
  line-height: 1.5;
}

.card .arrow {
  display: inline-block;
  margin-top: 14px;
  font-size: 0.85rem;
  color: var(--brand);
  font-weight: 500;
}

/* ── Collection page ── */
.collection-header {
  margin-bottom: 32px;
}

.collection-header h1 {
  font-size: 1.7rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.collection-header p {
  color: var(--muted);
}

.article-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.article-list a {
  display: flex;
  align-items: center;
  gap: 14px;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  text-decoration: none;
  color: var(--text);
  font-weight: 500;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.article-list a:hover {
  border-color: var(--brand);
  box-shadow: 0 2px 8px rgba(37,99,235,0.08);
}

.article-list .icon {
  font-size: 1.2rem;
  flex-shrink: 0;
}

/* ── Article page ── */
.article-header {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

.article-header h1 {
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.article-header .meta {
  color: var(--muted);
  font-size: 0.875rem;
}

/* ── Video embed ── */
.video-section {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 36px;
}

.video-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  background: #0f172a;
}

.video-wrapper iframe {
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  border: none;
}

.video-placeholder {
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: #94a3b8;
  gap: 10px;
  font-size: 0.9rem;
}

.video-placeholder .play-icon {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  border: 2px solid #475569;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
}

/* ── Article body ── */
.article-body {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
}

.article-body h2 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--brand-dark);
  margin: 28px 0 10px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

.article-body h2:first-child { margin-top: 0; }

.article-body p {
  margin-bottom: 14px;
  line-height: 1.7;
}

.article-body .step {
  display: flex;
  gap: 16px;
  margin-bottom: 18px;
  padding: 16px;
  background: var(--bg);
  border-radius: 6px;
  border-left: 3px solid var(--brand);
}

.article-body .step-num {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--brand);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.article-body .step-content strong {
  display: block;
  margin-bottom: 4px;
  font-weight: 600;
}

/* ── Footer ── */
footer {
  text-align: center;
  padding: 32px 24px;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
  margin-top: 60px;
}

/* ── Responsive ── */
@media (max-width: 600px) {
  .collections { grid-template-columns: 1fr; }
  .article-body { padding: 20px; }
  .hero h1 { font-size: 1.5rem; }
}