/* ============================================
   CSS Variables
   ============================================ */
:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #dbeafe;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --error-color: #ef4444;

    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;

    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;

    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;

    --transition: all 0.2s ease;
    --header-height: 70px;
    --sidebar-width: 280px;
}

[data-theme="dark"] {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --primary-light: #1e3a5f;

    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;

    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    --border-color: #334155;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* ============================================
   Header
   ============================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
    gap: 20px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
}

.logo i { font-size: 1.8rem; }

/* Search */
.search-container {
    position: relative;
    flex: 1;
    max-width: 400px;
}

.search-container > i {
    position: absolute;
    left: 15px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
}

.search-container input {
    width: 100%;
    padding: 12px 15px 12px 45px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.95rem;
    transition: var(--transition);
}

.search-container input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.search-results {
    position: absolute;
    top: calc(100% + 5px);
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    max-height: 400px;
    overflow-y: auto;
    display: none;
    z-index: 100;
}

.search-results.active { display: block; }

.search-result-item {
    padding: 12px 15px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.search-result-item:last-child { border-bottom: none; }
.search-result-item:hover { background: var(--bg-tertiary); }
.search-result-item.no-results {
    color: var(--text-muted);
    justify-content: center;
    cursor: default;
}

.search-result-item .unit-info { display: flex; flex-direction: column; }
.search-result-item .unit-name { font-weight: 500; }
.search-result-item .category-name { font-size: 0.8rem; color: var(--text-secondary); }
.search-result-item .unit-symbol {
    font-weight: 600;
    color: var(--primary-color);
    background: var(--primary-light);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
}

/* Navigation */
.nav {
    display: flex;
    gap: 5px;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: var(--transition);
}

.nav-link:hover, .nav-link.active {
    color: var(--primary-color);
    background: var(--primary-light);
}

/* Theme Toggle */
.theme-toggle {
    width: 44px;
    height: 44px;
    border: none;
    border-radius: var(--radius-md);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    font-size: 1.2rem;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background: var(--primary-light);
    color: var(--primary-color);
}

/* ============================================
   Main Layout
   ============================================ */
.main {
    margin-top: var(--header-height);
    padding: 30px 0;
    min-height: calc(100vh - var(--header-height));
}

.main > .container {
    display: flex;
    gap: 30px;
}

/* ============================================
   Sidebar
   ============================================ */
.sidebar {
    width: var(--sidebar-width);
    flex-shrink: 0;
    position: sticky;
    top: calc(var(--header-height) + 30px);
    height: fit-content;
    max-height: calc(100vh - var(--header-height) - 60px);
    overflow-y: auto;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: 20px;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header h3 { font-size: 1.1rem; font-weight: 600; }

.sidebar-toggle {
    display: none;
    background: var(--bg-tertiary);
    border: none;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    font-size: 1rem;
    color: var(--text-primary);
    cursor: pointer;
    align-items: center;
    justify-content: center;
}

.category-list { list-style: none; }
.category-item { margin-bottom: 4px; }

.category-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 15px;
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--radius-md);
    transition: var(--transition);
    font-weight: 500;
}

.category-link:hover { background: var(--bg-tertiary); color: var(--text-primary); }
.category-link.active { background: var(--primary-light); color: var(--primary-color); }
.category-link i { width: 20px; text-align: center; }

.category-link .unit-count {
    margin-left: auto;
    font-size: 0.75rem;
    background: var(--bg-tertiary);
    padding: 2px 8px;
    border-radius: 10px;
    color: var(--text-muted);
}

.category-link.active .unit-count { background: var(--primary-color); color: white; }

/* ============================================
   Content
   ============================================ */
.content { flex: 1; min-width: 0; }
.hidden { display: none !important; }

/* ============================================
   Converter Card
   ============================================ */
.converter-card {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    overflow: hidden;
}

.converter-header {
    padding: 25px 30px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    color: white;
}

.converter-header h1 { font-size: 1.75rem; margin-bottom: 5px; }
.converter-header p { opacity: 0.9; }

.converter-body {
    padding: 30px;
    display: flex;
    align-items: flex-end;
    gap: 20px;
    flex-wrap: wrap;
}

.conversion-section { flex: 1; min-width: 250px; }

.section-label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 10px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.input-group { display: flex; flex-direction: column; gap: 10px; }

.value-input {
    width: 100%;
    padding: 18px 20px;
    font-size: 1.5rem;
    font-weight: 600;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    background: var(--bg-secondary);
    color: var(--text-primary);
    transition: var(--transition);
}

.value-input:focus { outline: none; border-color: var(--primary-color); }

.value-input.result-input {
    background: var(--primary-light);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.unit-select {
    width: 100%;
    padding: 15px 20px;
    font-size: 1rem;
    font-weight: 500;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
}

.unit-select:focus { outline: none; border-color: var(--primary-color); }

/* Swap Button */
.swap-button {
    width: 50px;
    height: 50px;
    border: none;
    border-radius: 50%;
    background: var(--primary-color);
    color: white;
    font-size: 1.2rem;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    margin-bottom: 35px;
}

.swap-button:hover { background: var(--primary-hover); transform: rotate(180deg); }

/* Quick Actions */
.quick-actions {
    display: flex;
    gap: 10px;
    padding: 0 30px 20px;
    flex-wrap: wrap;
}

.action-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.action-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    background: var(--primary-light);
}

/* Formula Display */
.formula-display {
    padding: 20px 30px;
    background: var(--bg-tertiary);
    border-top: 1px solid var(--border-color);
}

.formula-display h4 {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.formula-display #formulaText {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
    font-family: 'Monaco', 'Consolas', monospace;
    margin-bottom: 5px;
}

.formula-description { font-size: 0.9rem; color: var(--text-secondary); }

/* ============================================
   Cards
   ============================================ */
.all-conversions-card,
.table-card,
.common-card {
    margin-top: 25px;
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    padding: 25px 30px;
}

.all-conversions-card h3,
.table-card h3,
.common-card h3 {
    font-size: 1.1rem;
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.all-conversions-card h3 i,
.table-card h3 i,
.common-card h3 i { color: var(--primary-color); }

.conversions-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 12px;
}

.conversion-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 15px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    cursor: pointer;
    transition: var(--transition);
}

.conversion-item:hover {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.conversion-item .unit-name { font-weight: 500; font-size: 0.9rem; }
.conversion-item .unit-value {
    font-weight: 600;
    color: var(--primary-color);
    font-family: 'Monaco', 'Consolas', monospace;
    font-size: 0.9rem;
}

.no-results { color: var(--text-muted); text-align: center; padding: 20px; }

/* Table */
.table-container { overflow-x: auto; }

.conversion-table { width: 100%; border-collapse: collapse; }

.conversion-table th,
.conversion-table td {
    padding: 12px 20px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

.conversion-table th {
    background: var(--bg-tertiary);
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    font-size: 0.8rem;
}

.conversion-table tbody tr:hover td { background: var(--bg-secondary); }
.conversion-table td:first-child { font-weight: 600; color: var(--primary-color); }

/* Common Grid */
.common-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 10px;
}

.common-link {
    display: block;
    padding: 15px 20px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 500;
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.common-link:hover {
    border-color: var(--primary-color);
    background: var(--primary-light);
    color: var(--primary-color);
}

.common-link i { margin-right: 8px; color: var(--primary-color); }

/* ============================================
   Pages
   ============================================ */
.page-header { margin-bottom: 30px; }
.page-header h1 { font-size: 2rem; margin-bottom: 10px; }
.page-header p { color: var(--text-secondary); }

.tables-selector {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
    margin-bottom: 30px;
    padding: 25px;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.tables-selector select { flex: 1; min-width: 180px; }

.btn-primary {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 15px 30px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-lg);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary:hover { background: var(--primary-hover); }

.generated-table-container {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: 25px;
}

.generated-table-header { margin-bottom: 20px; }
.generated-table-header h3 { font-size: 1.3rem; margin-bottom: 8px; }
.generated-table-header .formula-text {
    color: var(--primary-color);
    font-family: 'Monaco', 'Consolas', monospace;
    font-weight: 600;
}

.placeholder-text { color: var(--text-muted); text-align: center; padding: 40px; }

/* Formulas */
.formulas-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}

.formula-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: 25px;
    border-left: 4px solid var(--primary-color);
}

.formula-card h4 {
    font-size: 1rem;
    margin-bottom: 15px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.formula-card h4 i { color: var(--primary-color); }

.formula-card .formula {
    font-family: 'Monaco', 'Consolas', monospace;
    font-size: 1.1rem;
    color: var(--primary-color);
    padding: 15px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    margin-bottom: 12px;
}

.formula-card .example { font-size: 0.9rem; color: var(--text-secondary); }

/* ============================================
   Footer
   ============================================ */
.footer {
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    padding: 50px 0 30px;
    margin-top: 50px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h4 { font-size: 1.1rem; margin-bottom: 20px; }
.footer-section p { color: var(--text-secondary); line-height: 1.7; }

.footer-badges { display: flex; gap: 10px; margin-top: 15px; flex-wrap: wrap; }

.badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.badge i { color: var(--success-color); }

.footer-links { list-style: none; }
.footer-links li { margin-bottom: 10px; }
.footer-links a { color: var(--text-secondary); text-decoration: none; transition: var(--transition); }
.footer-links a:hover { color: var(--primary-color); }

.footer-bottom {
    text-align: center;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* ============================================
   Toast
   ============================================ */
.toast {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background: var(--success-color);
    color: white;
    padding: 15px 25px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: 10px;
    transform: translateY(100px);
    opacity: 0;
    transition: var(--transition);
    z-index: 9999;
}

.toast.show { transform: translateY(0); opacity: 1; }

/* ============================================
   Responsive
   ============================================ */
@media (max-width: 992px) {
    .header-content { flex-wrap: wrap; }
    .search-container { order: 3; max-width: 100%; width: 100%; margin-top: 10px; }
    .main > .container { flex-direction: column; }

    .sidebar { width: 100%; position: static; max-height: none; }
    .sidebar.collapsed .category-list { display: none; }
    .sidebar-toggle { display: flex; }

    .category-list {
        display: grid;
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
        gap: 8px;
        margin-top: 15px;
    }

    .converter-body { flex-direction: column; }
    .swap-button { align-self: center; margin-bottom: 0; transform: rotate(90deg); }
    .swap-button:hover { transform: rotate(270deg); }
    .conversion-section { width: 100%; min-width: 100%; }
}

@media (max-width: 768px) {
    .logo span { display: none; }
    .nav-link span { display: none; }
    .main { margin-top: 120px; padding: 15px 0; }
    .converter-header { padding: 20px; }
    .converter-header h1 { font-size: 1.4rem; }
    .converter-body { padding: 20px; }
    .value-input { font-size: 1.2rem; padding: 15px; }
    .quick-actions { padding: 0 20px 15px; }
    .all-conversions-card, .table-card, .common-card { padding: 20px; }
    .conversions-grid { grid-template-columns: 1fr; }
    .formulas-grid { grid-template-columns: 1fr; }
    .footer-content { grid-template-columns: 1fr; }
    .tables-selector { flex-direction: column; }
    .tables-selector select, .tables-selector button { width: 100%; }
}

@media (max-width: 480px) {
    .category-list { grid-template-columns: repeat(2, 1fr); }
    .category-link { flex-direction: column; text-align: center; padding: 12px 8px; gap: 5px; }
    .category-link .unit-count { display: none; }
    .action-btn span { display: none; }
    .common-grid { grid-template-columns: 1fr; }
    .toast { left: 20px; right: 20px; bottom: 20px; }
}

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

/* Hide number spinners */
input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
input[type="number"] { -moz-appearance: textfield; }