/**
 * Global Styles & Reset
 * Aesthetic: Plain white, crisp academic minimalist, high contrast, no neon, no emojis.
 */

:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-dim: #64748b;
  
  --border-light: #e2e8f0;
  --border-medium: #cbd5e1;
  --border-dark: #94a3b8;
  
  --focus-ring: #0284c7;
  
  /* Muted semantic accents - strictly for classification */
  --quark-accent: #4338ca;
  --quark-bg: #eef2ff;
  --quark-border: #c7d2fe;
  
  --lepton-accent: #047857;
  --lepton-bg: #ecfdf5;
  --lepton-border: #a7f3d0;
  
  --boson-accent: #b45309;
  --boson-bg: #fffbeb;
  --boson-border: #fde68a;
  
  --higgs-accent: #be123c;
  --higgs-bg: #fff1f2;
  --higgs-border: #fecdd3;
  
  --hadron-accent: #1d4ed8;
  --hadron-bg: #eff6ff;
  --hadron-border: #bfdbfe;
  
  --shadow-subtle: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-card: 0 1px 3px 0 rgba(0, 0, 0, 0.08), 0 1px 2px -1px rgba(0, 0, 0, 0.06);
  --shadow-drawer: -4px 0 24px rgba(0, 0, 0, 0.12);
  
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  
  --transition-fast: 150ms ease;
  --transition-normal: 240ms ease;
}

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

html {
  font-size: 16px;
  background-color: var(--bg-primary);
  color: var(--text-main);
  font-family: var(--font-sans);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.5;
}

/* Skip link for accessibility */
.skip-link {
  position: absolute;
  top: -40px;
  left: 1rem;
  background: var(--text-main);
  color: #fff;
  padding: 0.5rem 1rem;
  z-index: 1000;
  text-decoration: none;
  font-size: 0.875rem;
  border-radius: 4px;
}
.skip-link:focus {
  top: 1rem;
}

/* Layout Container */
.container {
  width: 100%;
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* Header & Navigation */
header.site-header {
  border-bottom: 1px solid var(--border-light);
  background: var(--bg-primary);
  padding: 2rem 0 1.5rem;
}

.header-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 1.5rem;
  margin-bottom: 1.25rem;
}

.brand-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  color: var(--text-main);
  line-height: 1.2;
}

.brand-subtitle {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-top: 0.35rem;
  max-width: 720px;
}

.header-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.badge-version {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  border: 1px solid var(--border-medium);
  border-radius: 4px;
  background: var(--bg-secondary);
  color: var(--text-muted);
}

.github-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.25rem 0.65rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-main);
  text-decoration: none;
  border: 1px solid var(--border-medium);
  border-radius: 4px;
  background: var(--bg-primary);
  transition: all var(--transition-fast);
}

.github-link:hover {
  background: var(--bg-secondary);
  border-color: var(--border-dark);
}

.github-icon {
  display: block;
}

/* Search & Filters Toolbar */
.toolbar-container {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  padding-top: 0.5rem;
}

.search-bar-wrap {
  position: relative;
  width: 100%;
  max-width: 600px;
}

.search-input {
  width: 100%;
  padding: 0.65rem 2.5rem 0.65rem 0.875rem;
  font-size: 0.9375rem;
  border: 1px solid var(--border-medium);
  border-radius: 6px;
  background-color: var(--bg-primary);
  color: var(--text-main);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-input:focus {
  border-color: var(--focus-ring);
  box-shadow: 0 0 0 3px rgba(2, 132, 199, 0.15);
}

.search-clear-btn {
  position: absolute;
  right: 0.6rem;
  top: 50%;
  transform: translateY(-50%);
  background: transparent;
  border: none;
  color: var(--text-dim);
  font-size: 1rem;
  cursor: pointer;
  padding: 0.25rem 0.5rem;
  display: none;
}
.search-clear-btn.visible {
  display: block;
}

/* Filter Pills */
.filter-pills-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}

.filter-btn {
  background: var(--bg-primary);
  border: 1px solid var(--border-medium);
  border-radius: 20px;
  padding: 0.35rem 0.85rem;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.filter-btn:hover {
  background: var(--bg-secondary);
  color: var(--text-main);
  border-color: var(--border-dark);
}

.filter-btn.active {
  background: var(--text-main);
  color: #ffffff;
  border-color: var(--text-main);
}

/* Learning Concept Callout */
.learning-callout {
  margin: 1.5rem 0;
  padding: 1rem 1.25rem;
  border: 1px solid var(--border-medium);
  border-left: 4px solid var(--text-main);
  background: var(--bg-secondary);
  border-radius: 4px;
}

.learning-callout-title {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-main);
  margin-bottom: 0.35rem;
}

.learning-callout-body {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.5;
}

.learning-callout-body strong {
  color: var(--text-main);
}

/* Main Content Area */
main.main-content {
  flex: 1;
  padding: 1.5rem 0 3.5rem;
}

/* Footer */
footer.site-footer {
  border-top: 1px solid var(--border-light);
  background: var(--bg-secondary);
  padding: 2.5rem 0;
  font-size: 0.8125rem;
  color: var(--text-muted);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.footer-col {
  max-width: 480px;
}

.footer-col h4 {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.footer-col p {
  margin-bottom: 0.5rem;
  line-height: 1.5;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 0.35rem;
}

.footer-links a, .footer-col a {
  color: var(--text-main);
  text-decoration: underline;
  text-underline-offset: 2px;
}
.footer-links a:hover, .footer-col a:hover {
  color: var(--focus-ring);
}

/* Accessibility utility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}