/* ============================================================
   PhysicsVault – Components Stylesheet
   components.css — Reusable UI components
   ============================================================ */

/* ── Hero Page Banner (non-homepage) ── */
.page-hero {
  background: var(--gradient-hero);
  padding: var(--space-16) 0;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
  position: relative;
  overflow: hidden;
}
.page-hero::before {
  content: '';
  position: absolute;
  width: 600px; height: 600px;
  background: radial-gradient(circle, rgba(124,140,255,0.08) 0%, transparent 70%);
  top: -200px; right: -100px;
  pointer-events: none;
}
.page-hero-title {
  font-size: clamp(var(--text-3xl), 5vw, var(--text-5xl));
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: var(--space-4);
}
.page-hero-subtitle {
  font-size: var(--text-xl);
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto;
}

/* ── Category Badge ── */
.category-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.badge-mechanics { background: rgba(124,140,255,0.12); color: #7c8cff; }
.badge-thermodynamics { background: rgba(251,146,60,0.12); color: #fb923c; }
.badge-waves { background: rgba(74,222,128,0.12); color: #4ade80; }
.badge-electro { background: rgba(250,204,21,0.12); color: #facc15; }
.badge-modern { background: rgba(192,132,252,0.12); color: #c084fc; }
.badge-kinematics { background: rgba(56,189,248,0.12); color: #38bdf8; }
.badge-quantum { background: rgba(248,113,113,0.12); color: #f87171; }

/* ── Filter Bar ── */
.filter-bar {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-4) var(--space-5);
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-bottom: var(--space-8);
}
.filter-label {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
}
.filter-btn {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all var(--transition-fast);
}
.filter-btn:hover, .filter-btn.active {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
}

/* ── Blog Listing Grid ── */
.blog-layout {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: var(--space-10);
  align-items: start;
}
.blog-sidebar { position: sticky; top: calc(var(--nav-height) + var(--space-6)); }

/* ── Pagination ── */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  margin-top: var(--space-10);
}
.page-btn {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all var(--transition-fast);
}
.page-btn:hover, .page-btn.active {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
}

/* ── Stats Bar ── */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-1);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  overflow: hidden;
  margin: var(--space-8) 0;
}
.stat-cell {
  text-align: center;
  padding: var(--space-6);
  border-right: 1px solid var(--color-border);
}
.stat-cell:last-child { border-right: none; }
.stat-number {
  font-size: var(--text-3xl);
  font-weight: 800;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: block;
}
.stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-top: var(--space-1);
}

/* ── Why PhysicsVault Section ── */
.feature-card {
  display: flex;
  gap: var(--space-4);
  padding: var(--space-5);
  background: var(--gradient-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  transition: all var(--transition-base);
}
.feature-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-border-light);
}
.feature-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  flex-shrink: 0;
}
.feature-icon-1 { background: rgba(124,140,255,0.15); }
.feature-icon-2 { background: rgba(247,201,72,0.15); }
.feature-icon-3 { background: rgba(74,222,128,0.15); }
.feature-icon-4 { background: rgba(251,146,60,0.15); }
.feature-icon-5 { background: rgba(192,132,252,0.15); }
.feature-icon-6 { background: rgba(56,189,248,0.15); }
.feature-text h3 {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}
.feature-text p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ── Formula Card ── */
.formula-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-5);
  transition: all var(--transition-base);
}
.formula-card:hover {
  border-color: var(--color-border-light);
  box-shadow: var(--shadow-md);
}
.formula-card-name {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-3);
}
.formula-card-eq {
  font-family: var(--font-mono);
  font-size: var(--text-xl);
  color: var(--color-primary);
  text-align: center;
  padding: var(--space-4);
  background: var(--color-bg);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-3);
  border: 1px solid var(--color-border);
}
.formula-card-desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.5;
}

/* ── Topic Overview Cards ── */
.topic-overview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-5);
}
.topic-overview-card {
  background: var(--gradient-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  text-decoration: none;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}
.topic-overview-card::after {
  content: '→';
  position: absolute;
  bottom: var(--space-5);
  right: var(--space-5);
  font-size: var(--text-xl);
  color: var(--color-text-subtle);
  transition: transform var(--transition-fast);
}
.topic-overview-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border-light);
}
.topic-overview-card:hover::after { transform: translateX(4px); }
.topic-ov-icon { font-size: 2rem; margin-bottom: var(--space-3); }
.topic-ov-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}
.topic-ov-articles {
  font-size: var(--text-sm);
  color: var(--color-primary);
  font-weight: 600;
  margin-bottom: var(--space-3);
}
.topic-ov-desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
}
.topic-ov-links { margin-top: var(--space-4); display: flex; flex-direction: column; gap: var(--space-1); }
.topic-ov-link {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}
.topic-ov-link:hover { color: var(--color-primary); }
.topic-ov-link::before { content: '•'; color: var(--color-primary); }

/* ── Contact Form ── */
.contact-form {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
}
.form-group { margin-bottom: var(--space-5); }
.form-label {
  display: block;
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}
.form-input, .form-textarea, .form-select {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text);
  font-size: var(--text-sm);
  font-family: var(--font-sans);
  outline: none;
  transition: border-color var(--transition-fast);
}
.form-input:focus, .form-textarea:focus, .form-select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(124,140,255,0.1);
}
.form-textarea { min-height: 160px; resize: vertical; }

/* ── Practice Question Card ── */
.question-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  margin-bottom: var(--space-5);
}
.question-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  margin-bottom: var(--space-4);
}
.question-num {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  background: var(--gradient-primary);
  color: white;
  font-size: var(--text-sm);
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.question-text {
  font-size: var(--text-base);
  color: var(--color-text);
  line-height: 1.6;
  flex: 1;
  font-family: var(--font-serif);
}
.question-difficulty {
  font-size: var(--text-xs);
  font-weight: 700;
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
}
.diff-easy { background: rgba(74,222,128,0.12); color: var(--color-success); }
.diff-medium { background: rgba(247,201,72,0.12); color: var(--color-accent); }
.diff-hard { background: rgba(248,113,113,0.12); color: var(--color-error); }
.question-options { list-style: none; display: flex; flex-direction: column; gap: var(--space-2); }
.option-btn {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text);
  font-size: var(--text-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: left;
  width: 100%;
}
.option-btn:hover { border-color: var(--color-primary); background: rgba(124,140,255,0.08); }
.option-btn.correct { border-color: var(--color-success); background: rgba(74,222,128,0.1); color: var(--color-success); }
.option-btn.incorrect { border-color: var(--color-error); background: rgba(248,113,113,0.1); color: var(--color-error); }
.option-letter {
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background: var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xs);
  font-weight: 700;
  flex-shrink: 0;
}
.question-explanation {
  display: none;
  margin-top: var(--space-4);
  padding: var(--space-4);
  background: rgba(74,222,128,0.07);
  border: 1px solid rgba(74,222,128,0.2);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-text);
  line-height: 1.6;
}

/* ── Notice / Alert ── */
.alert {
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-md);
  border-left: 3px solid;
  font-size: var(--text-sm);
  line-height: 1.5;
}
.alert-info { background: rgba(56,189,248,0.08); border-color: var(--color-info); color: var(--color-info); }
.alert-success { background: rgba(74,222,128,0.08); border-color: var(--color-success); color: var(--color-success); }
.alert-warning { background: rgba(247,201,72,0.08); border-color: var(--color-accent); color: var(--color-accent); }

/* ── Loading Spinner ── */
.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Section Divider ── */
.section-divider {
  width: 60px;
  height: 4px;
  background: var(--gradient-primary);
  border-radius: var(--radius-full);
  margin: var(--space-4) auto;
}

/* ── Scroll to Top ── */
#scroll-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 44px;
  height: 44px;
  background: var(--gradient-primary);
  color: white;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  cursor: pointer;
  opacity: 0;
  transform: translateY(10px);
  transition: all var(--transition-base);
  z-index: 500;
}
#scroll-top.visible { opacity: 1; transform: translateY(0); }
#scroll-top:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }

/* ── Formula Sheet Layout ── */
.formula-sheet-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-5);
}
.formula-section-title {
  font-size: var(--text-2xl);
  font-weight: 700;
  color: var(--color-text);
  margin: var(--space-10) 0 var(--space-5);
  padding-bottom: var(--space-3);
  border-bottom: 2px solid var(--color-border);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* ── Comparison Table ── */
.compare-table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-sm);
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
}
.compare-table th {
  background: var(--gradient-primary);
  color: white;
  padding: var(--space-3) var(--space-4);
  text-align: center;
  font-weight: 700;
}
.compare-table th:first-child { text-align: left; }
.compare-table td {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text-muted);
}
.compare-table td:first-child { font-weight: 600; color: var(--color-text); }
.compare-table tr:hover td { background: var(--color-surface); }
.compare-table tr:last-child td { border-bottom: none; }

/* ── Responsive Components ── */
@media (max-width: 1024px) {
  .blog-layout { grid-template-columns: 1fr; }
  .blog-sidebar { position: static; }
  .stats-bar { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 640px) {
  .stats-bar { grid-template-columns: 1fr 1fr; }
  .formula-sheet-grid { grid-template-columns: 1fr; }
  .contact-form { padding: var(--space-5); }
}