/* ============================================================
   STYLE.CSS — Unit Converter Pro
   ============================================================ */

/* ---------- CSS Variables (Light & Dark) ---------- */
:root {
  --primary: #2563EB;
  --primary-dark: #1D4ED8;
  --primary-light: #EFF6FF;
  --secondary: #0EA5E9;
  --accent: #10B981;
  --accent-light: #D1FAE5;
  --bg: #F8FAFC;
  --bg-card: #FFFFFF;
  --bg-input: #F1F5F9;
  --text: #0F172A;
  --text-secondary: #475569;
  --text-muted: #94A3B8;
  --border: #E2E8F0;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.06);
  --shadow-hover: 0 12px 40px rgba(0, 0, 0, 0.10);
  --radius: 16px;
  --radius-sm: 8px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --header-bg: rgba(255, 255, 255, 0.85);
  --glass-bg: rgba(255, 255, 255, 0.70);
  --toast-bg: #1E293B;
  --toast-text: #F8FAFC;
}

[data-theme="dark"] {
  --bg: #0F172A;
  --bg-card: #1E293B;
  --bg-input: #334155;
  --text: #F1F5F9;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  --border: #334155;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-hover: 0 12px 40px rgba(0, 0, 0, 0.5);
  --header-bg: rgba(15, 23, 42, 0.90);
  --glass-bg: rgba(30, 41, 59, 0.70);
  --primary-light: #1E293B;
  --accent-light: #1E293B;
  --toast-bg: #F1F5F9;
  --toast-text: #0F172A;
}

/* ---------- Reset & Base ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  transition: background var(--transition), color var(--transition);
  line-height: 1.6;
  min-height: 100vh;
  padding-top: 72px;
}

a {
  color: var(--primary);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

img {
  max-width: 100%;
  height: auto;
}

/* ---------- Skip Link ---------- */
.skip-link {
  position: absolute;
  top: -100%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--primary);
  color: #fff;
  padding: 0.75rem 1.5rem;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  z-index: 10000;
  font-weight: 600;
}
.skip-link:focus {
  top: 0;
}

/* ---------- Scrollbar ---------- */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg);
}
::-webkit-scrollbar-thumb {
  background: var(--primary);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--primary-dark);
}

/* ---------- Header ---------- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--header-bg);
  backdrop-filter: blur(16px) saturate(180%);
  -webkit-backdrop-filter: blur(16px) saturate(180%);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
  height: 72px;
  display: flex;
  align-items: center;
}

.header-inner {
  max-width: 1280px;
  width: 100%;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
}
.logo-icon {
  font-size: 1.6rem;
}
.logo span {
  color: var(--primary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.theme-toggle {
  background: var(--bg-input);
  border: none;
  border-radius: 50%;
  width: 44px;
  height: 44px;
  font-size: 1.25rem;
  cursor: pointer;
  transition: background var(--transition), transform 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text);
}
.theme-toggle:hover {
  background: var(--border);
  transform: scale(1.05);
}
.theme-toggle:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* Mobile menu toggle */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.6rem;
  cursor: pointer;
  color: var(--text);
  padding: 4px;
}
.menu-toggle:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* Navigation */
.nav {
  display: flex;
  align-items: center;
  gap: 8px;
}
.nav a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.9rem;
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  transition: background var(--transition), color var(--transition);
  text-decoration: none;
}
.nav a:hover {
  background: var(--bg-input);
  color: var(--text);
  text-decoration: none;
}
.nav a.active {
  color: var(--primary);
  background: var(--primary-light);
}

/* ---------- Main ---------- */
.main {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 24px 40px;
}

/* ---------- Hero ---------- */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}
.hero h1 {
  font-size: clamp(2.2rem, 6vw, 4rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.1;
  margin-bottom: 8px;
  color: var(--text);
}
.hero h1 span {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero p {
  font-size: clamp(1rem, 2vw, 1.3rem);
  color: var(--text-secondary);
  margin-bottom: 24px;
}

/* ---------- Search ---------- */
.search-wrap {
  max-width: 560px;
  margin: 0 auto 32px;
  position: relative;
}
.search-wrap input {
  width: 100%;
  padding: 16px 20px 16px 52px;
  border: 2px solid var(--border);
  border-radius: 50px;
  font-size: 1rem;
  background: var(--bg-card);
  color: var(--text);
  transition: border-color var(--transition), box-shadow var(--transition), background var(--transition);
  outline: none;
  font-family: var(--font);
}
.search-wrap input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.15);
}
.search-wrap input::placeholder {
  color: var(--text-muted);
}
.search-icon {
  position: absolute;
  left: 18px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.3rem;
  color: var(--text-muted);
  pointer-events: none;
}
.search-clear {
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  font-size: 1.2rem;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px;
  display: none;
  border-radius: 50%;
}
.search-clear:hover {
  background: var(--bg-input);
}
.search-clear.visible {
  display: block;
}

/* ---------- Category Grid ---------- */
.categories {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 16px;
  margin-top: 8px;
}

.category-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 16px;
  text-align: center;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition), background var(--transition);
  box-shadow: var(--shadow);
  text-decoration: none;
  color: var(--text);
  display: block;
}
.category-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
  border-color: var(--primary);
}
.category-card:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}
.category-card .cat-icon {
  font-size: 2.2rem;
  margin-bottom: 6px;
  display: block;
}
.category-card .cat-name {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text);
}
.category-card .cat-count {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 2px;
}

/* ---------- Converter Panel ---------- */
.converter-panel {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow);
  margin-top: 32px;
  transition: background var(--transition), border-color var(--transition), box-shadow var(--transition);
  display: none;
  animation: fadeSlideUp 0.4s ease;
}
.converter-panel.active {
  display: block;
}

@keyframes fadeSlideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 20px;
}
.panel-header h2 {
  font-size: 1.4rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 10px;
}
.panel-header h2 .cat-icon-small {
  font-size: 1.6rem;
}
.panel-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.panel-actions button {
  background: var(--bg-input);
  border: none;
  border-radius: var(--radius-sm);
  padding: 8px 14px;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--transition), transform 0.2s;
  color: var(--text);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font);
}
.panel-actions button:hover {
  background: var(--border);
  transform: scale(1.02);
}
.panel-actions button:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}
.panel-actions button .btn-icon {
  font-size: 1.1rem;
}

.fav-btn.active {
  color: #F59E0B;
  background: #FEF3C7;
}
[data-theme="dark"] .fav-btn.active {
  background: #422006;
  color: #FBBF24;
}

/* Converter rows */
.converter-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 12px;
  align-items: end;
  margin-bottom: 16px;
}
.converter-row .field {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.converter-row .field label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.converter-row .field input,
.converter-row .field select {
  padding: 12px 14px;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 1rem;
  background: var(--bg-input);
  color: var(--text);
  transition: border-color var(--transition), box-shadow var(--transition), background var(--transition);
  font-family: var(--font);
  width: 100%;
  min-width: 0;
}
.converter-row .field input:focus,
.converter-row .field select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
  outline: none;
}
.converter-row .field input {
  background: var(--bg-card);
}
.converter-row .field select {
  cursor: pointer;
  appearance: auto;
}

.swap-btn {
  background: var(--primary);
  border: none;
  border-radius: 50%;
  width: 48px;
  height: 48px;
  font-size: 1.3rem;
  cursor: pointer;
  transition: transform 0.3s, background var(--transition), box-shadow var(--transition);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-bottom: 2px;
  align-self: center;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}
.swap-btn:hover {
  transform: rotate(180deg);
  background: var(--primary-dark);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}
.swap-btn:focus-visible {
  outline: 2px solid var(--text);
  outline-offset: 2px;
}

.result-display {
  background: var(--primary-light);
  border-radius: var(--radius-sm);
  padding: 16px 20px;
  margin: 8px 0 16px;
  text-align: center;
  border: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}
.result-display .result-value {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary);
  word-break: break-all;
}
.result-display .result-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.converter-bottom {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 8px;
  justify-content: center;
}
.converter-bottom button {
  padding: 10px 20px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), transform 0.2s, box-shadow var(--transition);
  font-family: var(--font);
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.converter-bottom button:hover {
  transform: translateY(-2px);
}
.converter-bottom button:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}
.btn-primary:hover {
  background: var(--primary-dark);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

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

.btn-success {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
}
.btn-success:hover {
  background: #059669;
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--border);
  color: var(--text);
}
.btn-outline:hover {
  background: var(--bg-input);
}

.btn-danger {
  background: #EF4444;
  color: #fff;
}
.btn-danger:hover {
  background: #DC2626;
}

/* ---------- Recent & Favorites ---------- */
.history-section {
  margin-top: 32px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  box-shadow: var(--shadow);
  transition: background var(--transition), border-color var(--transition);
}
.history-section h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.history-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
  max-height: 200px;
  overflow-y: auto;
}
.history-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 12px;
  background: var(--bg-input);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  transition: background var(--transition);
}
.history-item .h-value {
  font-weight: 600;
  color: var(--primary);
}
.history-item .h-meta {
  color: var(--text-secondary);
  font-size: 0.8rem;
}
.history-item .h-del {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  padding: 0 4px;
}
.history-item .h-del:hover {
  color: #EF4444;
}

.empty-state {
  color: var(--text-muted);
  font-size: 0.9rem;
  padding: 8px 0;
}

/* ---------- Back to Top ---------- */
.back-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  box-shadow: 0 4px 20px rgba(37, 99, 235, 0.4);
  transition: transform 0.3s, opacity 0.3s, visibility 0.3s, background var(--transition);
  opacity: 0;
  visibility: hidden;
  transform: scale(0.8);
  z-index: 900;
  display: flex;
  align-items: center;
  justify-content: center;
}
.back-top.visible {
  opacity: 1;
  visibility: visible;
  transform: scale(1);
}
.back-top:hover {
  background: var(--primary-dark);
  transform: scale(1.05);
}
.back-top:focus-visible {
  outline: 2px solid var(--text);
  outline-offset: 2px;
}

/* ---------- Footer ---------- */
.footer {
  background: var(--bg-card);
  border-top: 1px solid var(--border);
  padding: 40px 24px 24px;
  margin-top: 48px;
  transition: background var(--transition), border-color var(--transition);
}
.footer-inner {
  max-width: 1280px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 32px;
}
.footer h4 {
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text);
}
.footer a {
  display: block;
  color: var(--text-secondary);
  font-size: 0.85rem;
  padding: 4px 0;
  transition: color var(--transition);
  text-decoration: none;
}
.footer a:hover {
  color: var(--primary);
  text-decoration: underline;
}
.footer .copyright {
  grid-column: 1 / -1;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.8rem;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  margin-top: 8px;
}

/* ---------- Toast ---------- */
.toast-container {
  position: fixed;
  bottom: 90px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 9999;
  pointer-events: none;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  max-width: 90vw;
}
.toast {
  background: var(--toast-bg);
  color: var(--toast-text);
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 500;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
  pointer-events: auto;
  animation: toastIn 0.3s ease;
  transition: opacity 0.3s, transform 0.3s;
  backdrop-filter: blur(8px);
  text-align: center;
}
.toast.out {
  opacity: 0;
  transform: translateY(20px) scale(0.95);
}

@keyframes toastIn {
  from {
    opacity: 0;
    transform: translateY(20px) scale(0.95);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

/* ---------- Responsive ---------- */
@media (max-width: 768px) {
  body {
    padding-top: 64px;
  }
  .header {
    height: 64px;
  }
  .header-inner {
    padding: 0 16px;
  }
  .logo {
    font-size: 1.05rem;
  }
  .logo-icon {
    font-size: 1.3rem;
  }

  .menu-toggle {
    display: block;
  }
  .nav {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 16px;
    gap: 4px;
    display: none;
    box-shadow: var(--shadow);
    backdrop-filter: blur(16px);
  }
  .nav.open {
    display: flex;
  }
  .nav a {
    width: 100%;
    padding: 10px 16px;
    font-size: 1rem;
  }

  .hero {
    padding: 24px 0 16px;
  }
  .hero h1 {
    font-size: 2rem;
  }

  .categories {
    grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
    gap: 12px;
  }
  .category-card {
    padding: 16px 12px;
  }
  .category-card .cat-icon {
    font-size: 1.8rem;
  }

  .converter-panel {
    padding: 20px 16px;
  }
  .converter-row {
    grid-template-columns: 1fr;
    gap: 8px;
  }
  .swap-btn {
    width: 40px;
    height: 40px;
    font-size: 1rem;
    align-self: center;
    margin: 4px 0;
  }
  .panel-header {
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
  }
  .panel-header h2 {
    font-size: 1.2rem;
  }
  .panel-actions {
    flex-wrap: wrap;
  }
  .panel-actions button {
    padding: 6px 12px;
    font-size: 0.8rem;
  }
  .result-display .result-value {
    font-size: 1.4rem;
  }
  .converter-bottom {
    gap: 8px;
  }
  .converter-bottom button {
    padding: 8px 16px;
    font-size: 0.8rem;
  }

  .history-section {
    padding: 16px;
  }

  .footer-inner {
    grid-template-columns: 1fr 1fr;
    gap: 24px;
  }
  .footer .copyright {
    grid-column: 1 / -1;
  }

  .back-top {
    bottom: 20px;
    right: 20px;
    width: 44px;
    height: 44px;
    font-size: 1.2rem;
  }

  .toast {
    font-size: 0.85rem;
    padding: 10px 18px;
  }
}

@media (max-width: 480px) {
  .categories {
    grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
    gap: 10px;
  }
  .category-card {
    padding: 12px 8px;
  }
  .category-card .cat-icon {
    font-size: 1.5rem;
  }
  .category-card .cat-name {
    font-size: 0.8rem;
  }
  .converter-panel {
    padding: 16px 12px;
  }
  .converter-row .field input,
  .converter-row .field select {
    padding: 10px 12px;
    font-size: 0.9rem;
  }
  .result-display .result-value {
    font-size: 1.2rem;
  }
  .footer-inner {
    grid-template-columns: 1fr;
    gap: 16px;
  }
}

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

.hidden {
  display: none !important;
}

.text-center {
  text-align: center;
}
.mt-8 {
  margin-top: 8px;
}
.mt-16 {
  margin-top: 16px;
}
.gap-8 {
  gap: 8px;
}
.flex-wrap {
  display: flex;
  flex-wrap: wrap;
}
.items-center {
  align-items: center;
}
.justify-center {
  justify-content: center;
}

/* ---------- Loading Skeleton ---------- */
.skeleton {
  background: linear-gradient(90deg, var(--bg-input) 25%, var(--border) 50%, var(--bg-input) 75%);
  background-size: 200% 100%;
  animation: skeletonShimmer 1.5s infinite;
  border-radius: var(--radius-sm);
}
@keyframes skeletonShimmer {
  0% {
    background-position: 200% 0;
  }
  100% {
    background-position: -200% 0;
  }
}

/* ---------- Print ---------- */
@media print {
  .header,
  .back-top,
  .toast-container,
  .footer {
    display: none !important;
  }
  body {
    padding-top: 0;
    background: #fff;
    color: #000;
  }
  .converter-panel {
    border: 1px solid #ccc;
    box-shadow: none;
    background: #fff;
  }
}