/* ============================================================
   style.css — Toolybird Complete Design System
   ============================================================ */

/* ---- CSS Custom Properties -------------------------------- */
:root {
  /* Brand */
  --primary:        #6C63FF;
  --primary-dark:   #5A52E0;
  --primary-light:  #EDE9FE;
  --secondary:      #00D9FF;
  --accent:         #FF6584;
  --success:        #10B981;
  --warning:        #F59E0B;
  --danger:         #EF4444;

  /* Light Mode Surfaces */
  --bg-primary:     #F8FAFC;
  --bg-secondary:   #EFF2F7;
  --card-bg:        #FFFFFF;
  --text-primary:   #1E293B;
  --text-secondary: #64748B;
  --text-muted:     #94A3B8;
  --border:         #E2E8F0;
  --shadow-sm:      0 1px 3px rgba(0,0,0,.08);
  --shadow-md:      0 4px 16px rgba(0,0,0,.10);
  --shadow-lg:      0 8px 32px rgba(0,0,0,.12);

  /* Radius */
  --r-sm:   6px;
  --r-md:   10px;
  --r-lg:   16px;
  --r-xl:   24px;
  --r-pill: 9999px;

  /* Spacing */
  --sp-xs:  4px;
  --sp-sm:  8px;
  --sp-md:  16px;
  --sp-lg:  24px;
  --sp-xl:  32px;
  --sp-2xl: 48px;
  --sp-3xl: 64px;

  /* Typography */
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  /* Category Colors */
  --cat-chemistry:   #6C63FF;
  --cat-physics:     #00D9FF;
  --cat-diy:         #F59E0B;
  --cat-math:        #10B981;
  --cat-photography: #EF4444;
  --cat-music:       #EC4899;
  --cat-developer:   #8B5CF6;
  --cat-text:        #06B6D4;
  --cat-generators:  #F97316;
  --cat-time:        #3B82F6;
  --cat-baking:      #D97706;

  /* Transitions */
  --trans-fast:  150ms ease;
  --trans-base:  250ms ease;
  --trans-slow:  350ms ease;
}

/* ---- CSS Reset ------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  transition: background var(--trans-base), color var(--trans-base);
}
img, svg { display: block; max-width: 100%; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: none; }
button, input, select, textarea { font-family: inherit; font-size: 1rem; }
ul, ol { list-style: none; }

/* ---- Typography ------------------------------------------ */
h1 { font-size: clamp(1.75rem, 4vw, 2.5rem); font-weight: 700; line-height: 1.2; }
h2 { font-size: clamp(1.25rem, 3vw, 1.75rem); font-weight: 700; line-height: 1.3; }
h3 { font-size: 1.125rem; font-weight: 600; }
h4 { font-size: 1rem; font-weight: 600; }
p  { margin-bottom: var(--sp-md); color: var(--text-secondary); }
p:last-child { margin-bottom: 0; }

/* ---- Layout ---------------------------------------------- */
.container   { max-width: 1280px; margin: 0 auto; padding: 0 var(--sp-lg); }
.container-sm{ max-width: 860px;  margin: 0 auto; padding: 0 var(--sp-lg); }

/* ---- Site Header ----------------------------------------- */
.site-header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 8px rgba(0,0,0,.06);
}
.header-inner {
  display: grid;
  grid-template-columns: auto 1fr auto auto;
  align-items: center;
  height: 64px;
  gap: var(--sp-lg);
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-primary);
  text-decoration: none;
  white-space: nowrap;
  letter-spacing: -.02em;
}
.logo-icon {
  width: 36px; height: 36px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  border-radius: var(--r-md);
  display: grid;
  place-items: center;
  color: #fff;
  font-size: 1.1rem;
  box-shadow: 0 2px 8px rgba(108,99,255,.35);
  flex-shrink: 0;
}
.logo span { color: var(--primary); }
.logo:hover { text-decoration: none; }

/* Header Search */
.header-search {
  position: relative;
  min-width: 0;
}
.header-search input {
  width: 100%;
  height: 42px;
  padding: 0 70px 0 44px;
  border: 1.5px solid var(--border);
  border-radius: var(--r-pill);
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.9rem;
  transition: border-color var(--trans-fast), background var(--trans-fast), box-shadow var(--trans-fast);
}
.header-search input:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--card-bg);
  box-shadow: 0 0 0 3px rgba(108,99,255,.12);
}
.header-search .search-icon {
  position: absolute;
  left: 15px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  pointer-events: none;
  font-size: 1rem;
}
.search-kbd {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.6875rem;
  font-family: var(--font-mono);
  color: var(--text-muted);
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 2px 5px;
  pointer-events: none;
  white-space: nowrap;
}
.header-search input:focus ~ .search-kbd { display: none; }
.search-results-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 0; right: 0;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  box-shadow: var(--shadow-lg);
  max-height: 400px;
  overflow-y: auto;
  z-index: 200;
  display: none;
}
.search-results-dropdown.open { display: block; }
.search-result-item {
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  padding: 10px 16px;
  cursor: pointer;
  transition: background var(--trans-fast);
}
.search-result-item:hover { background: var(--bg-secondary); }
.search-result-item .icon { font-size: 1.2rem; }
.search-result-item .info strong { display: block; font-size: 0.875rem; }
.search-result-item .info span  { font-size: 0.75rem; color: var(--text-muted); }

/* Header Nav Links (desktop) */
.header-nav {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-shrink: 0;
}
.header-nav-link {
  display: inline-flex;
  align-items: center;
  padding: 7px 14px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--r-md);
  transition: color var(--trans-fast), background var(--trans-fast);
  white-space: nowrap;
}
.header-nav-link:hover, .header-nav-link.active {
  color: var(--primary);
  background: var(--primary-light);
  text-decoration: none;
}

/* Header Actions (mobile toggle) */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  flex-shrink: 0;
}
.btn-icon {
  width: 40px; height: 40px;
  border: none;
  border-radius: var(--r-md);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  cursor: pointer;
  display: grid;
  place-items: center;
  font-size: 1.1rem;
  transition: background var(--trans-fast), color var(--trans-fast);
}
.btn-icon:hover { background: var(--primary-light); color: var(--primary); }

/* Mobile Nav Toggle — hidden on desktop */
.nav-toggle  { display: none; }
#search-toggle { display: none; }

/* Mobile-only nav items */
.nav-mobile-only { display: none; }

/* ---- Main Navigation ------------------------------------- */
.main-nav {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  overflow-x: auto;
  scrollbar-width: none;
}
.main-nav::-webkit-scrollbar { display: none; }
.nav-list {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 8px var(--sp-lg);
  min-width: min-content;
  margin: 0 auto;
}
.nav-item a {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 13px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-secondary);
  white-space: nowrap;
  border-radius: var(--r-pill);
  border: 1.5px solid transparent;
  transition: background var(--trans-fast), color var(--trans-fast), border-color var(--trans-fast);
}
.nav-item a:hover {
  background: var(--bg-secondary);
  color: var(--item-accent, var(--primary));
  border-color: var(--border);
  text-decoration: none;
}
.nav-item a.active {
  background: var(--item-accent, var(--primary));
  color: #fff;
  border-color: transparent;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(108,99,255,.3);
}

/* ---- Buttons --------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-sm);
  padding: 10px 20px;
  min-height: 48px;
  border: none;
  border-radius: var(--r-md);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--trans-fast);
  text-decoration: none;
}
.btn-primary {
  background: var(--primary);
  color: #fff;
}
.btn-primary:hover { background: var(--primary-dark); color: #fff; text-decoration: none; transform: translateY(-1px); box-shadow: 0 4px 12px rgba(108,99,255,.35); }
.btn-secondary {
  background: transparent;
  color: var(--primary);
  border: 1.5px solid var(--primary);
}
.btn-secondary:hover { background: var(--primary-light); text-decoration: none; }
.btn-ghost {
  background: var(--bg-secondary);
  color: var(--text-secondary);
}
.btn-ghost:hover { background: var(--border); color: var(--text-primary); text-decoration: none; }
.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { background: #DC2626; text-decoration: none; }
.btn-sm { padding: 6px 14px; min-height: 36px; font-size: 0.8rem; }
.btn-lg { padding: 14px 28px; min-height: 56px; font-size: 1rem; }
.btn-full { width: 100%; }
.btn:focus-visible,
.btn-icon:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }

/* ---- Cards ----------------------------------------------- */
.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-xl);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--trans-base), transform var(--trans-base), border-color var(--trans-base);
}
.card:hover { box-shadow: var(--shadow-md); }

/* Tool Card (catalog grid) */
.tool-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-lg);
  display: flex;
  flex-direction: column;
  gap: var(--sp-sm);
  transition: all var(--trans-base);
  position: relative;
  overflow: hidden;
  text-decoration: none;
  color: var(--text-primary);
}
.tool-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  right: 0;
  height: 3px;
  background: var(--primary);
  opacity: 0;
  transition: opacity var(--trans-fast);
}
.tool-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); border-color: var(--primary); text-decoration: none; }
.tool-card:hover::before { opacity: 1; }
.tool-card .tool-icon { font-size: 2rem; margin-bottom: var(--sp-xs); }
.tool-card h3 { font-size: 0.95rem; font-weight: 600; color: var(--text-primary); margin: 0; }
.tool-card p  { font-size: 0.8rem; color: var(--text-secondary); margin: 0; }

/* Small Related Tool Card */
.tool-card-small {
  display: flex;
  align-items: center;
  gap: var(--sp-md);
  padding: var(--sp-md);
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  text-decoration: none;
  color: var(--text-primary);
  transition: all var(--trans-fast);
}
.tool-card-small:hover { border-color: var(--primary); background: var(--primary-light); text-decoration: none; }
.tool-card-small .tool-icon { font-size: 1.5rem; flex-shrink: 0; }
.tool-card-small strong { display: block; font-size: 0.875rem; }
.tool-card-small p { font-size: 0.775rem; color: var(--text-muted); margin: 0; }

/* Category Badge */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: var(--r-pill);
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.badge-primary { background: var(--primary-light); color: var(--primary); }
.badge-success { background: #D1FAE5; color: #065F46; }

/* ---- Tools Grid ------------------------------------------ */
.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: var(--sp-lg);
}
.tools-grid-sm {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--sp-md);
}

/* ---- Tool Page Layout ------------------------------------ */
.tool-page {
  padding: var(--sp-xl) 0 var(--sp-3xl);
}
.tool-page-grid {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: var(--sp-xl);
  align-items: start;
}
.tool-main { min-width: 0; }
.tool-sidebar { display: flex; flex-direction: column; gap: var(--sp-lg); }

/* Tool Calculator Card */
.calc-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-xl);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}
.calc-card-header {
  padding: var(--sp-xl);
  border-bottom: 1px solid var(--border);
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--card-bg) 100%);
}
.calc-card-header h1 { margin-bottom: var(--sp-sm); }
.calc-card-header p  { margin: 0; font-size: 0.9rem; color: var(--text-secondary); }
.calc-card-body { padding: var(--sp-xl); }

/* ---- Form Elements --------------------------------------- */
.form-group {
  margin-bottom: var(--sp-lg);
}
.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--sp-sm);
}
.form-label .unit {
  font-weight: 400;
  color: var(--text-muted);
  margin-left: 4px;
}
.form-control {
  width: 100%;
  height: 48px;
  padding: 0 var(--sp-md);
  border: 1.5px solid var(--border);
  border-radius: var(--r-md);
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.95rem;
  transition: border-color var(--trans-fast), box-shadow var(--trans-fast);
}
.form-control:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(108,99,255,.12);
  background: var(--card-bg);
}
.form-control.error { border-color: var(--danger); }
textarea.form-control { height: auto; padding: 12px var(--sp-md); resize: vertical; min-height: 120px; }
select.form-control { cursor: pointer; }

.form-hint { font-size: 0.775rem; color: var(--text-muted); margin-top: var(--sp-xs); }
.form-error { font-size: 0.775rem; color: var(--danger); margin-top: var(--sp-xs); display: none; }
.form-error.visible { display: block; }

/* Input Row */
.input-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--sp-md);
}
.input-row-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-md);
}

/* Form Actions */
.form-actions {
  display: flex;
  gap: var(--sp-sm);
  flex-wrap: wrap;
  margin-top: var(--sp-lg);
}

/* ---- Result Display -------------------------------------- */
.result-card {
  background: linear-gradient(135deg, var(--primary-light), var(--bg-secondary));
  border: 1.5px solid var(--primary);
  border-radius: var(--r-lg);
  padding: var(--sp-xl);
  margin-top: var(--sp-lg);
  display: none;
  animation: fadeIn .3s ease;
}
.result-card.show { display: block; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
@keyframes resultFlash { 0%,100% { box-shadow: var(--shadow-md); } 40% { box-shadow: 0 0 0 4px rgba(108,99,255,.35), var(--shadow-lg); transform: scale(1.01); } }
.result-card.flash { animation: resultFlash .5s ease; }

.result-main {
  display: flex;
  align-items: baseline;
  gap: var(--sp-sm);
  margin-bottom: var(--sp-sm);
}
.result-value {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 700;
  color: var(--primary);
  font-variant-numeric: tabular-nums;
}
.result-unit { font-size: 1.1rem; color: var(--text-secondary); font-weight: 500; }
.result-label { font-size: 0.85rem; color: var(--text-muted); }
.result-details { margin-top: var(--sp-md); }
.result-detail-item {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.875rem;
}
.result-detail-item:last-child { border-bottom: none; }
.result-detail-item .label { color: var(--text-secondary); }
.result-detail-item .value { font-weight: 600; color: var(--text-primary); }

/* Error Message */
.error-message {
  background: #FEF2F2;
  border: 1px solid #FECACA;
  border-radius: var(--r-md);
  padding: var(--sp-md);
  color: var(--danger);
  font-size: 0.875rem;
  display: none;
  margin-top: var(--sp-md);
}
.error-message.show { display: block; }

/* Copy / Download Actions */
.result-actions {
  display: flex;
  gap: var(--sp-sm);
  margin-top: var(--sp-md);
  flex-wrap: wrap;
}

/* ---- Textarea Tool Pair ---------------------------------- */
.textarea-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--sp-lg);
}
.textarea-box { display: flex; flex-direction: column; gap: var(--sp-sm); }
.textarea-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: .05em;
}
.textarea-box textarea {
  flex: 1;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  min-height: 240px;
}

/* ---- Content Sections ------------------------------------ */
.content-section {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-xl);
  margin-top: var(--sp-xl);
}
.content-section h2 { margin-bottom: var(--sp-md); }
.content-section p  { color: var(--text-secondary); line-height: 1.7; }

.steps-list { counter-reset: step; margin-top: var(--sp-md); }
.step-item {
  display: flex;
  gap: var(--sp-md);
  margin-bottom: var(--sp-md);
}
.step-num {
  width: 32px; height: 32px;
  background: var(--primary);
  color: #fff;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 0.8rem;
  font-weight: 700;
  flex-shrink: 0;
  margin-top: 2px;
}
.step-item p { margin: 0; }

/* Formula Display */
.formula-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-left: 4px solid var(--primary);
  border-radius: var(--r-md);
  padding: var(--sp-md) var(--sp-lg);
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--text-primary);
  margin: var(--sp-md) 0;
  overflow-x: auto;
}

/* ---- FAQ Section ----------------------------------------- */
.faq-section {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-xl);
  margin-top: var(--sp-xl);
}
.faq-section h2 { margin-bottom: var(--sp-lg); }
.faq-list { display: flex; flex-direction: column; gap: var(--sp-sm); }
.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  overflow: hidden;
  transition: border-color var(--trans-fast);
}
.faq-item[open] { border-color: var(--primary); }
.faq-item summary {
  padding: var(--sp-md) var(--sp-lg);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: var(--bg-secondary);
  transition: background var(--trans-fast);
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after { content: '+'; font-size: 1.3rem; color: var(--primary); transition: transform var(--trans-fast); }
.faq-item[open] summary::after { transform: rotate(45deg); }
.faq-item[open] summary { background: var(--primary-light); color: var(--primary); }
.faq-item p { padding: var(--sp-md) var(--sp-lg); color: var(--text-secondary); font-size: 0.9rem; line-height: 1.7; margin: 0; }

/* ---- Related Tools Section ------------------------------- */
.related-tools {
  margin-top: var(--sp-xl);
}
.related-tools h2 { margin-bottom: var(--sp-lg); }
.related-tools .tools-grid { grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); }

/* ---- Breadcrumb ------------------------------------------ */
.breadcrumb {
  padding: var(--sp-sm) 0;
  margin-bottom: var(--sp-lg);
}
.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--sp-xs);
  font-size: 0.825rem;
}
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb span { color: var(--text-muted); }
.breadcrumb [aria-current="page"] { color: var(--text-primary); font-weight: 500; }

/* ---- Hero Section (index.php) ---------------------------- */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, #A855F7 100%);
  padding: var(--sp-3xl) 0;
  text-align: center;
  color: #fff;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.04'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E") repeat;
}
.hero-content { position: relative; z-index: 1; }
.hero h1 { font-size: clamp(2rem, 5vw, 3.5rem); margin-bottom: var(--sp-md); color: #fff; }
.hero p   { font-size: clamp(1rem, 2vw, 1.2rem); opacity: .9; max-width: 600px; margin: 0 auto var(--sp-xl); color: rgba(255,255,255,.9); }
.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--sp-xl);
  flex-wrap: wrap;
  margin-top: var(--sp-xl);
}
.hero-stat { text-align: center; }
.hero-stat .num { font-size: 2rem; font-weight: 700; display: block; }
.hero-stat .lbl { font-size: 0.875rem; opacity: .8; }
.hero-search {
  max-width: 560px;
  margin: 0 auto;
  position: relative;
}
.hero-search input {
  width: 100%;
  height: 56px;
  padding: 0 60px 0 20px;
  border: none;
  border-radius: var(--r-pill);
  background: rgba(255,255,255,.95);
  color: var(--text-primary);
  font-size: 1rem;
  box-shadow: 0 8px 32px rgba(0,0,0,.15);
}
.hero-search input:focus { outline: none; background: #fff; }
.hero-search button {
  position: absolute;
  right: 6px;
  top: 6px;
  height: 44px;
  padding: 0 20px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--r-pill);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--trans-fast);
}
.hero-search button:hover { background: var(--primary-dark); }

/* ---- Category Cards (index) ------------------------------ */
.categories-section { padding: var(--sp-3xl) 0; }
.categories-section h2 { text-align: center; margin-bottom: var(--sp-2xl); }
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--sp-lg);
}
.category-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-xl);
  text-align: center;
  text-decoration: none;
  color: var(--text-primary);
  transition: all var(--trans-base);
  position: relative;
  overflow: hidden;
}
.category-card::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 4px;
  background: var(--cat-color, var(--primary));
  transform: scaleX(0);
  transition: transform var(--trans-base);
}
.category-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); text-decoration: none; }
.category-card:hover::after { transform: scaleX(1); }
.category-card .cat-icon { font-size: 2.5rem; margin-bottom: var(--sp-md); }
.category-card h3 { font-size: 1rem; margin-bottom: var(--sp-xs); }
.category-card .count { font-size: 0.8rem; color: var(--text-muted); }

/* ---- Popular Tools Section ------------------------------- */
.popular-section { padding: var(--sp-3xl) 0; background: var(--bg-secondary); }
.popular-section h2 { margin-bottom: var(--sp-2xl); }
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--sp-xl);
}

/* ---- Recently Used (local storage) ----------------------- */
.recent-section { padding: var(--sp-xl) 0; }

/* ---- Sidebar Widgets ------------------------------------- */
.sidebar-widget {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--sp-lg);
}
.sidebar-widget h3 { margin-bottom: var(--sp-md); font-size: 1rem; }
.sidebar-tool-list { display: flex; flex-direction: column; gap: var(--sp-sm); }
.sidebar-tool-link {
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  font-size: 0.875rem;
  color: var(--text-secondary);
  padding: 6px 8px;
  border-radius: var(--r-sm);
  transition: all var(--trans-fast);
  text-decoration: none;
}
.sidebar-tool-link:hover { background: var(--bg-secondary); color: var(--primary); text-decoration: none; }

/* ---- Footer ---------------------------------------------- */
/* ---- Footer ---------------------------------------------- */
.site-footer {
  margin-top: var(--sp-3xl);
}
.footer-top {
  background: #0F172A;
  padding: var(--sp-3xl) 0 var(--sp-2xl);
  border-top: 3px solid var(--primary);
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.8fr repeat(4, 1fr);
  gap: var(--sp-xl);
}
/* Brand col */
.footer-logo { color: #fff; }
.footer-logo span { color: var(--secondary); }
.footer-brand p {
  font-size: 0.875rem;
  color: #94A3B8;
  margin-top: var(--sp-md);
  line-height: 1.7;
}
.footer-category-icons {
  display: flex;
  gap: var(--sp-sm);
  margin-top: var(--sp-lg);
  flex-wrap: wrap;
}
.footer-category-icons a {
  font-size: 1.25rem;
  text-decoration: none;
  transition: transform var(--trans-fast), filter var(--trans-fast);
  display: inline-block;
}
.footer-category-icons a:hover { transform: scale(1.2); filter: drop-shadow(0 0 6px rgba(108,99,255,.6)); }
/* Link cols */
.footer-col-heading {
  font-size: 0.8125rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: #fff;
  margin-bottom: var(--sp-md);
  padding-left: 10px;
  border-left: 3px solid var(--col-accent, var(--primary));
}
.footer-col ul { display: flex; flex-direction: column; gap: 10px; }
.footer-col a {
  font-size: 0.875rem;
  color: #94A3B8;
  transition: color var(--trans-fast), padding-left var(--trans-fast);
  display: inline-block;
}
.footer-col a:hover {
  color: #fff;
  padding-left: 4px;
  text-decoration: none;
}
/* Bottom bar */
.footer-bottom {
  background: #070E1A;
  border-top: 1px solid rgba(255,255,255,.06);
  padding: var(--sp-md) 0;
}
.footer-bottom-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--sp-md);
}
.footer-copy, .footer-tagline { font-size: 0.8rem; color: #475569; }
.footer-bottom-links { display: flex; gap: var(--sp-md); }
.footer-bottom-links a {
  font-size: 0.8rem;
  color: #64748B;
  transition: color var(--trans-fast);
}
.footer-bottom-links a:hover { color: var(--primary); text-decoration: none; }

/* ---- Toast / Notifications ------------------------------- */
.toast-container {
  position: fixed;
  bottom: var(--sp-xl);
  right: var(--sp-xl);
  z-index: 500;
  display: flex;
  flex-direction: column;
  gap: var(--sp-sm);
}
.toast {
  background: var(--text-primary);
  color: var(--card-bg);
  padding: 12px 20px;
  border-radius: var(--r-md);
  font-size: 0.875rem;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  animation: toastIn .3s ease;
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
}
.toast.success { background: var(--success); }
.toast.error   { background: var(--danger); }
@keyframes toastIn { from { opacity: 0; transform: translateX(20px); } to { opacity: 1; transform: translateX(0); } }

/* ---- Print Styles ---------------------------------------- */
@media print {
  .site-header, .site-footer, .main-nav, .breadcrumb, .form-actions,
  .result-actions, .sidebar-widget, .header-search, .btn { display: none !important; }
  .tool-page-grid { grid-template-columns: 1fr; }
  .content-section, .faq-section, .result-card { box-shadow: none; border: 1px solid #ddd; }
  body { background: #fff; color: #000; }
  .result-value { color: #000; }
  .worksheet-content { font-size: 14pt; }
  .worksheet-problem { page-break-inside: avoid; }
}

/* ---- Worksheet Styles ------------------------------------ */
.worksheet-content { padding: var(--sp-xl); }
.worksheet-header { text-align: center; margin-bottom: var(--sp-xl); }
.worksheet-header h2 { font-size: 1.5rem; }
.worksheet-meta { display: flex; justify-content: space-between; border-bottom: 2px solid var(--text-primary); padding-bottom: var(--sp-sm); margin-bottom: var(--sp-xl); }
.worksheet-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--sp-xl) var(--sp-2xl);
}
.worksheet-problem { margin-bottom: var(--sp-lg); }
.worksheet-problem .prob-num { font-size: 0.8rem; color: var(--text-muted); margin-bottom: var(--sp-xs); }
.worksheet-problem .prob-text { font-size: 1.1rem; font-weight: 600; }
.answer-line { border-bottom: 1.5px solid var(--text-secondary); min-width: 120px; display: inline-block; margin-left: var(--sp-sm); }

/* ---- Metronome ------------------------------------------- */
.metronome-display {
  text-align: center;
  padding: var(--sp-2xl);
  background: var(--bg-secondary);
  border-radius: var(--r-lg);
  margin-bottom: var(--sp-lg);
}
.beat-indicator {
  width: 80px; height: 80px;
  background: var(--primary);
  border-radius: 50%;
  margin: 0 auto var(--sp-lg);
  transition: transform .1s ease, background .1s ease;
  box-shadow: 0 0 0 0 rgba(108,99,255,.4);
}
.beat-indicator.pulse {
  animation: beat .1s ease;
}
@keyframes beat {
  0%   { transform: scale(1); box-shadow: 0 0 0 0 rgba(108,99,255,.5); }
  50%  { transform: scale(1.15); box-shadow: 0 0 0 20px rgba(108,99,255,0); }
  100% { transform: scale(1); box-shadow: 0 0 0 0 rgba(108,99,255,0); }
}
.bpm-display { font-size: 3rem; font-weight: 700; color: var(--primary); }

/* ---- Color Swatch ---------------------------------------- */
.color-swatch {
  width: 100%; height: 80px;
  border-radius: var(--r-md);
  margin-bottom: var(--sp-md);
  border: 1px solid var(--border);
  transition: background .15s ease;
}

/* ---- Responsive Breakpoints ------------------------------ */
@media (max-width: 1024px) {
  .tool-page-grid { grid-template-columns: 1fr; }
  .tool-sidebar { display: grid; grid-template-columns: 1fr 1fr; }
  .footer-grid { grid-template-columns: repeat(3, 1fr); }
  .footer-brand { grid-column: 1 / -1; }
}

@media (max-width: 768px) {
  .container { padding: 0 var(--sp-md); }
  /* Header: logo | search-hidden | actions (3-col: auto auto auto) */
  .header-inner { grid-template-columns: auto 1fr auto; gap: var(--sp-sm); }
  .header-search { display: none; }
  .header-search.mobile-open {
    display: block;
    position: absolute; top: 64px; left: 0; right: 0;
    padding: var(--sp-md);
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    z-index: 99;
  }
  .header-search.mobile-open input { padding-right: var(--sp-md); }
  .search-kbd { display: none; }
  .header-nav { display: none; }
  .nav-toggle { display: grid; }
  #search-toggle { display: grid; }
  /* Category nav becomes vertical dropdown on mobile */
  .main-nav { display: none; overflow: visible; }
  .main-nav.open { display: block; }
  .nav-list {
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
    padding: var(--sp-sm) 0;
    min-width: unset;
    gap: 2px;
  }
  .nav-item a {
    border-radius: 0;
    border: none;
    border-left: 3px solid transparent;
    padding: 11px var(--sp-md);
    font-size: 0.9375rem;
    box-shadow: none;
  }
  .nav-item a:hover {
    border-color: transparent;
    border-left-color: var(--item-accent, var(--primary));
    background: var(--bg-secondary);
    color: var(--item-accent, var(--primary));
  }
  .nav-item a.active {
    background: var(--primary-light);
    color: var(--item-accent, var(--primary));
    border-left-color: var(--item-accent, var(--primary));
    border-radius: 0;
    box-shadow: none;
  }
  .nav-mobile-only { display: list-item; }
  .hero { padding: var(--sp-2xl) 0; }
  .hero-stats { gap: var(--sp-lg); }
  .textarea-pair { grid-template-columns: 1fr; }
  .input-row, .input-row-3 { grid-template-columns: 1fr; }
  .tools-grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: var(--sp-md); }
  .category-grid { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
  .tool-sidebar { grid-template-columns: 1fr; }
  .worksheet-grid { grid-template-columns: 1fr; }
  .section-header { flex-direction: column; align-items: flex-start; gap: var(--sp-sm); }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 1.75rem; }
  .hero-search input { height: 48px; }
  .hero-search button { height: 36px; padding: 0 14px; font-size: 0.85rem; }
  .calc-card-body { padding: var(--sp-lg); }
  .form-actions { flex-direction: column; }
  .form-actions .btn { width: 100%; }
  .result-value { font-size: 2rem; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer-bottom-inner { flex-direction: column; text-align: center; gap: var(--sp-sm); }
  .footer-tagline { display: none; }
}

/* ---- Utility Classes ------------------------------------- */
.text-center { text-align: center; }
.text-muted   { color: var(--text-muted); }
.text-primary { color: var(--primary); }
.text-success { color: var(--success); }
.text-danger  { color: var(--danger); }
.mt-sm  { margin-top: var(--sp-sm); }
.mt-md  { margin-top: var(--sp-md); }
.mt-lg  { margin-top: var(--sp-lg); }
.mt-xl  { margin-top: var(--sp-xl); }
.mb-md  { margin-bottom: var(--sp-md); }
.mb-lg  { margin-bottom: var(--sp-lg); }
.d-flex { display: flex; }
.gap-sm { gap: var(--sp-sm); }
.gap-md { gap: var(--sp-md); }
.align-center { align-items: center; }
.justify-between { justify-content: space-between; }
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); border: 0; }