/* Base resets */
:root {
  --bg: #f5f7fb;
  --bg-solid: #ffffff;
  --text: #1a2433;
  --muted: #5b677a;
  --primary: #4f46e5;
  --primary-2: #7c3aed;
  --accent: #06b6d4;
  --border: rgba(15, 23, 42, 0.08);
  --shadow: 0 10px 30px rgba(79, 70, 229, 0.12);
}

body.dark {
  --bg: #0f172a;
  --bg-solid: #111827;
  --text: #f8fafc;
  --muted: #b6c2d4;
  --primary: #8b5cf6;
  --primary-2: #22d3ee;
  --accent: #14b8a6;
  --border: rgba(255, 255, 255, 0.08);
  --shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: linear-gradient(180deg, rgba(79, 70, 229, 0.12), transparent), var(--bg);
  color: var(--text);
  transition: background 0.25s ease, color 0.25s ease;
}

a { color: inherit; text-decoration: none; }
button, input, select, textarea { font: inherit; }

.container { width: min(1180px, calc(100% - 2rem)); margin: 0 auto; }
.section-block { padding: 4rem 0; }
.sr-only { position: absolute; left: -9999px; }

.topbar {
  background: linear-gradient(90deg, var(--primary), var(--primary-2));
  color: white;
  padding: 0.65rem 0;
}
.topbar-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.theme-toggle, .menu-toggle, .btn-icon, .back-to-top {
  border: none; cursor: pointer;
}
.theme-toggle {
  padding: 0.5rem 0.8rem;
  border-radius: 999px;
  background: white;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  backdrop-filter: blur(14px);
  background: rgba(245, 247, 251, 0.85);
  border-bottom: 1px solid var(--border);
}
body.dark .site-header { background: rgba(15, 23, 42, 0.9); }
.nav-wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.9rem 0;
}
.brand {
  font-size: 1.45rem;
  font-weight: 700;
  color: var(--primary);
}
.main-nav {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}
.main-nav a {
  padding: 0.5rem 0.7rem;
  border-radius: 999px;
  color: var(--muted);
}
.main-nav a:hover, .main-nav a.active { background: rgba(79, 70, 229, 0.12); color: var(--primary); }
.menu-toggle { display: none; background: transparent; font-size: 1.25rem; }

.hero-section {
  display: grid;
  grid-template-columns: 1.4fr 0.9fr;
  gap: 1.5rem;
  padding: 4rem 0 2rem;
  align-items: center;
}
.hero-copy h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  line-height: 1.1;
  margin: 0.2rem 0 1rem;
}
.hero-copy p { color: var(--muted); }
.eyebrow { color: var(--primary); font-weight: 700; text-transform: uppercase; letter-spacing: 0.12em; }
.search-panel input, .calc-form input, .calc-form select, .calc-form textarea {
  width: 100%;
  padding: 0.9rem 1rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg-solid);
  color: var(--text);
}
.search-panel { margin-top: 1rem; }
.hero-actions, .button-row, .result-actions { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.8rem 1.1rem;
  border-radius: 12px;
  border: 1px solid transparent;
  transition: transform 0.2s ease, opacity 0.2s ease;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary { background: linear-gradient(90deg, var(--primary), var(--primary-2)); color: white; }
.btn-secondary { background: rgba(6, 182, 212, 0.12); color: var(--accent); }
.btn-outline { background: transparent; border-color: var(--border); }
.btn-icon {
  background: rgba(79, 70, 229, 0.1);
  color: var(--primary);
  border-radius: 10px;
  padding: 0.45rem 0.6rem;
}

.card {
  background: var(--bg-solid);
  border-radius: 22px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}
.hero-card, .mini-card, .calculator-card, .sidebar-panel, .about-card, .contact-card, .about-page-card, .contact-page-card {
  padding: 1.25rem;
}

.stat-item {
  display: flex;
  justify-content: space-between;
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--border);
}
.stat-item:last-child { border-bottom: 0; }

.section-heading { margin-bottom: 1rem; }
.section-heading h2 { margin: 0 0 0.3rem; }
.section-heading p { color: var(--muted); margin: 0; }
.categories-grid, .card-grid, .about-grid, .contact-grid {
  display: grid;
  gap: 1rem;
}
.categories-grid { grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); }
.category-card, .mini-card {
  background: var(--bg-solid);
  border-radius: 18px;
  border: 1px solid var(--border);
  padding: 1rem;
  transition: transform 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}
.category-card:hover, .mini-card:hover { transform: translateY(-2px); }
.category-card.active {
  border-color: rgba(79, 70, 229, 0.5);
  box-shadow: var(--shadow);
  background: linear-gradient(180deg, rgba(79, 70, 229, 0.12), transparent);
}
.category-card span { display: block; font-weight: 700; }
.category-card small { color: var(--muted); }

.popular-grid, .recent-grid { grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); }
.calculator-layout {
  display: grid;
  grid-template-columns: minmax(0, 2fr) 320px;
  gap: 1.5rem;
}
.calculator-list { display: grid; gap: 1.5rem; }
.category-group {
  display: grid;
  gap: 1rem;
  padding: 1rem;
  border-radius: 20px;
  border: 1px solid var(--border);
  background: rgba(79, 70, 229, 0.04);
  scroll-margin-top: 6.5rem;
}
.category-group-header h3 {
  margin: 0;
  font-size: 1.3rem;
}
.calc-form { display: grid; gap: 1rem; }
.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.9rem;
}
.label { display: grid; gap: 0.4rem; }
.result-card {
  margin-top: 0.5rem;
  border-radius: 18px;
  background: linear-gradient(180deg, rgba(79, 70, 229, 0.08), transparent);
  padding: 1rem;
}
.result-card p.animate-result {
  transform: scale(1.02);
  transition: transform 0.25s ease;
}
.result-heading {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.6rem;
}
.sidebar-panel ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.favorite-list li, .history-list li {
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--border);
}
.favorite-list li:last-child, .history-list li:last-child { border-bottom: none; }

.faq-list { display: grid; gap: 0.75rem; }
.faq-item {
  border: 1px solid var(--border);
  border-radius: 15px;
  padding: 1rem;
  background: var(--bg-solid);
}

.site-footer {
  padding: 1.2rem 0 2rem;
  text-align: center;
  color: var(--muted);
}

.back-to-top {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  padding: 0.8rem 1rem;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--primary), var(--primary-2));
  color: white;
  display: none;
}
.back-to-top.show { display: inline-flex; }

.loader {
  position: fixed;
  inset: 0;
  background: rgba(255,255,255,0.9);
  display: grid;
  place-items: center;
  z-index: 1000;
}
body.dark .loader { background: rgba(15,23,42,0.92); }
.loader-ring {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  border: 4px solid rgba(79,70,229,0.2);
  border-top: 4px solid var(--primary);
  animation: spin 1s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

.toast {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  background: var(--bg-solid);
  color: var(--text);
  border: 1px solid var(--border);
  padding: 0.9rem 1rem;
  border-radius: 12px;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(10px);
  transition: all 0.25s ease;
}
.toast.show { opacity: 1; transform: translateY(0); }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation: none !important; transition: none !important; }
}