/* AI Skills Hub — Layout */

.app-shell { min-height: 100vh; display: flex; flex-direction: column; }

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: var(--surface-card); border-bottom: 1px solid hsl(var(--hue),5%,90%);
  padding: 0 var(--space-md); height: var(--header-h);
  display: flex; align-items: center; justify-content: space-between; gap: var(--space-sm);
}
.site-header .logo { font-size: var(--text-lg); font-weight: 700; color: var(--color-primary); }
.header-actions { display: flex; align-items: center; gap: var(--space-sm); }
.btn-icon { width: 36px; height: 36px; display: flex; align-items: center; justify-content: center; border-radius: var(--radius-full); font-size: 1.2rem; }

/* Main content */
.site-main { flex: 1; padding: var(--space-md); max-width: var(--content-max); margin: 0 auto; width: 100%; }
@media (max-width: 767px) { .site-main { padding-bottom: calc(var(--bottom-nav-h) + var(--space-md)); } }

/* Bottom nav (mobile only) */
.bottom-nav {
  display: flex; position: fixed; bottom: 0; left: 0; right: 0; z-index: 100;
  background: var(--surface-card); border-top: 1px solid hsl(var(--hue),5%,90%);
  height: var(--bottom-nav-h); justify-content: space-around; align-items: center;
}
.bottom-nav a { display: flex; flex-direction: column; align-items: center; gap: 2px; font-size: var(--text-xs); color: var(--text-tertiary); padding: var(--space-xs); }
.bottom-nav a.active { color: var(--color-primary); }
.bottom-nav a span { font-size: 1.3rem; }
@media (min-width: 768px) { .bottom-nav { display: none; } }

/* Tool Grid */
.tool-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--space-sm); }
@media (min-width: 600px) { .tool-grid { grid-template-columns: repeat(3, 1fr); } }
@media (min-width: 1024px) { .tool-grid { grid-template-columns: repeat(4, 1fr); } }

/* Sections */
.section { margin: var(--space-lg) 0; }
.section h2 { margin-bottom: var(--space-sm); }
.section-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: var(--space-sm); }
.section-header a { font-size: var(--text-sm); color: var(--color-primary); }

/* Breadcrumb */
.breadcrumb { display: flex; gap: 4px; font-size: var(--text-sm); color: var(--text-tertiary); margin-bottom: var(--space-md); flex-wrap: wrap; }
.breadcrumb a { color: var(--text-secondary); }
.breadcrumb-sep { color: var(--text-tertiary); margin: 0 4px; }

/* Category scroll */
.category-scroll { display: flex; gap: var(--space-sm); overflow-x: auto; padding: var(--space-sm) 0; scroll-snap-type: x mandatory; -webkit-overflow-scrolling: touch; }
.category-scroll::-webkit-scrollbar { display: none; }
.category-chip { display: flex; align-items: center; gap: 6px; padding: 10px 18px; border-radius: var(--radius-full); background: var(--surface-card); border: 1px solid hsl(var(--hue),5%,85%); font-size: var(--text-sm); font-weight: 500; white-space: nowrap; scroll-snap-align: start; transition: all var(--dur-fast); }
.category-chip:hover { border-color: var(--color-primary); background: var(--color-primary-light); }
.chip-icon { font-size: 1.2rem; }

/* Hero */
.hero { text-align: center; padding: var(--space-2xl) var(--space-md); }
.hero h1 { font-size: var(--text-3xl); margin-bottom: var(--space-sm); }
.hero p { color: var(--text-secondary); margin-bottom: var(--space-lg); }
.search-bar { display: flex; gap: var(--space-xs); max-width: 500px; margin: 0 auto; }
.search-bar input { flex: 1; }

/* Category hero */
.category-hero { text-align: center; padding: var(--space-xl) var(--space-md); border-radius: var(--radius-lg); margin-bottom: var(--space-lg); }
.category-hero-icon { font-size: 3rem; display: block; margin-bottom: var(--space-sm); }
.category-hero h1 { font-size: var(--text-2xl); }
.category-hero p { color: var(--text-secondary); }

/* Content sections */
.content-section { margin: var(--space-xl) 0; }
.content-section h2 { margin-bottom: var(--space-md); padding-bottom: var(--space-xs); border-bottom: 2px solid var(--color-primary-light); }
.prose { line-height: 1.9; color: var(--text-secondary); }
.prose p { margin-bottom: var(--space-md); }

/* Detail TOC */
.detail-toc { display: flex; gap: var(--space-xs); overflow-x: auto; padding: var(--space-sm) 0; position: sticky; top: var(--header-h); background: var(--surface-ground); z-index: 10; }
.detail-toc::-webkit-scrollbar { display: none; }
.detail-toc a { padding: 6px 14px; font-size: var(--text-sm); color: var(--text-secondary); border-radius: var(--radius-full); white-space: nowrap; transition: all var(--dur-fast); }
.detail-toc a:hover { background: var(--color-primary-light); color: var(--color-primary); }

/* Progress bar */
.progress-bar { position: fixed; top: 0; left: 0; height: 3px; background: var(--color-accent); z-index: 200; transition: width 0.2s; border-radius: 0 2px 2px 0; }

/* Lightbox */
.lightbox-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.9); z-index: 999; display: flex; align-items: center; justify-content: center; padding: var(--space-lg); }
.lightbox-content { position: relative; max-width: 90vw; max-height: 90vh; }
.lightbox-content img { max-height: 85vh; object-fit: contain; border-radius: var(--radius-md); }
.lightbox-close { position: absolute; top: -40px; right: 0; font-size: 2rem; color: white; }
.lightbox-content p { color: white; text-align: center; margin-top: var(--space-sm); }

/* Empty / Error */
.empty-state, .error-state { text-align: center; padding: var(--space-2xl); }
.empty-state p, .error-state p { color: var(--text-secondary); margin-bottom: var(--space-md); }

/* Footer */
.site-footer { text-align: center; padding: var(--space-lg); color: var(--text-tertiary); font-size: var(--text-sm); border-top: 1px solid hsl(var(--hue),5%,90%); margin-top: var(--space-2xl); }