/* ==========================================================================
   SandSpan.com — Complete Stylesheet
   Mobile-first, theme-aware, accessible, ad-friendly
   ========================================================================== */

/* ---------- CSS Custom Properties (Light Theme) ---------- */
:root {
    /* Colors */
    --color-bg: #f5faff;
    --color-surface: #ffffff;
    --color-surface-hover: #f0f6ff;
    --color-border: #d6e4f5;
    --color-border-focus: #8ab8f0;
    --color-text: #0f1f33;
    --color-text-secondary: #4a5b73;
    --color-text-muted: #7a8ba3;
    --color-primary: #1a73e8;
    --color-primary-hover: #1557b0;
    --color-primary-light: #e8f1fd;
    --color-accent: #f59e0b;
    --color-accent-hover: #d97706;
    --color-accent-light: #fef3c7;
    --color-teal: #0d9488;
    --color-teal-light: #ccfbf1;
    --color-success: #059669;
    --color-success-bg: #d1fae5;
    --color-danger: #dc2626;
    --color-gradient-start: #1a73e8;
    --color-gradient-end: #0d9488;

    /* Typography */
    --font-display: 'DM Serif Display', 'Georgia', 'Times New Roman', serif;
    --font-body: 'Inter', 'Nunito', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'SF Mono', 'Menlo', 'Consolas', 'Courier New', monospace;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;
    --font-size-5xl: 3.5rem;
    --line-height-tight: 1.15;
    --line-height-normal: 1.6;

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

    /* Borders & Radii */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
    --border-width: 1.5px;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(15, 31, 51, 0.06);
    --shadow-md: 0 4px 16px rgba(15, 31, 51, 0.08);
    --shadow-lg: 0 12px 40px rgba(15, 31, 51, 0.12);
    --shadow-glow: 0 0 0 3px rgba(26, 115, 232, 0.3);

    /* Layout */
    --header-height: 64px;
    --sidebar-width: 170px;
    --max-width: 1320px;
    --content-max-width: 720px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 400ms ease;
}

/* ---------- Dark Theme ---------- */
[data-theme="dark"] {
    --color-bg: #0a111f;
    --color-surface: #111d32;
    --color-surface-hover: #182940;
    --color-border: #1f3354;
    --color-border-focus: #3b5998;
    --color-text: #e4ecfa;
    --color-text-secondary: #b0c0dc;
    --color-text-muted: #7a8aa8;
    --color-primary: #5b9cf5;
    --color-primary-hover: #7ab4f8;
    --color-primary-light: #1a2d4a;
    --color-accent: #fbbf24;
    --color-accent-hover: #f59e0b;
    --color-accent-light: #3b2f12;
    --color-teal: #2dd4bf;
    --color-teal-light: #133a37;
    --color-success: #34d399;
    --color-success-bg: #0f3328;
    --color-gradient-start: #5b9cf5;
    --color-gradient-end: #2dd4bf;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.6);
    --shadow-glow: 0 0 0 3px rgba(91, 156, 245, 0.4);
}

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

html {
    -webkit-text-size-adjust: 100%;
    -moz-text-size-adjust: 100%;
    text-size-adjust: 100%;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--color-text);
    background: var(--color-bg);
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    overflow-x: hidden;
}

img, svg { max-width: 100%; display: block; }
a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }
ul, ol { list-style: none; }
input, select, textarea { font-family: inherit; font-size: inherit; }

/* ---------- Focus Styles ---------- */
:focus-visible {
    outline: none;
    box-shadow: var(--shadow-glow);
    border-radius: var(--radius-sm);
}

/* ---------- Screen Reader Only ---------- */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ---------- Skip Link ---------- */
.skip-link {
    position: absolute;
    top: -9999px;
    left: -9999px;
    background: var(--color-primary);
    color: #fff;
    padding: 12px 20px;
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: var(--font-size-base);
    z-index: 1000;
}
.skip-link:focus {
    top: 12px;
    left: 12px;
}

/* ---------- Header ---------- */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: saturate(180%) blur(16px);
    -webkit-backdrop-filter: saturate(180%) blur(16px);
    border-bottom: var(--border-width) solid var(--color-border);
}
[data-theme="dark"] .site-header {
    background: rgba(17, 29, 50, 0.85);
}
.header-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-lg);
    display: flex;
    align-items: center;
    height: var(--header-height);
    gap: var(--space-md);
}

/* Logo */
.logo {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--color-text);
    font-weight: 800;
    font-size: var(--font-size-lg);
    text-decoration: none;
    flex-shrink: 0;
}
.logo:hover { text-decoration: none; }
.logo-icon {
    width: 36px;
    height: 36px;
    border-radius: 10px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    color: #fff;
    display: grid;
    place-items: center;
    font-weight: 800;
    font-size: var(--font-size-lg);
}
.logo-text {
    letter-spacing: -0.02em;
}

/* Main Navigation */
.main-nav {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    margin-left: auto;
}
.nav-link {
    color: var(--color-text-secondary);
    padding: 10px 16px;
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: var(--font-size-sm);
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    transition: background var(--transition-fast), color var(--transition-fast);
    text-decoration: none;
}
.nav-link:hover,
.nav-link.active {
    background: var(--color-primary-light);
    color: var(--color-primary);
    text-decoration: none;
}

/* Theme Toggle */
.theme-toggle-btn {
    width: 44px;
    height: 44px;
    border-radius: var(--radius-full);
    border: var(--border-width) solid var(--color-border);
    background: var(--color-surface);
    display: grid;
    place-items: center;
    font-size: 1.2rem;
    transition: border-color var(--transition-fast), background var(--transition-fast);
    cursor: pointer;
}
.theme-toggle-btn:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
}
.theme-icon { pointer-events: none; }

/* Mobile Menu Button */
.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 10px;
    width: 44px;
    height: 44px;
    justify-content: center;
    align-items: center;
    border-radius: var(--radius-sm);
    border: var(--border-width) solid var(--color-border);
    background: var(--color-surface);
    margin-left: auto;
    z-index: 110;
}
.hamburger-line {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--color-text);
    border-radius: 2px;
    transition: transform var(--transition-normal), opacity var(--transition-normal);
}
.mobile-menu-btn[aria-expanded="true"] .hamburger-line:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}
.mobile-menu-btn[aria-expanded="true"] .hamburger-line:nth-child(2) {
    opacity: 0;
}
.mobile-menu-btn[aria-expanded="true"] .hamburger-line:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ---------- Hero ---------- */
.hero {
    background: linear-gradient(160deg, #0d2b5e 0%, #0f3d7a 30%, #115199 60%, #1a73e8 100%);
    padding: var(--space-3xl) var(--space-lg) var(--space-2xl);
    text-align: center;
    position: relative;
    overflow: hidden;
}
.hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background:
        radial-gradient(ellipse 600px 300px at 20% 20%, rgba(255, 255, 255, 0.06) 0%, transparent 60%),
        radial-gradient(ellipse 500px 250px at 80% 60%, rgba(13, 148, 136, 0.12) 0%, transparent 60%),
        radial-gradient(ellipse 400px 200px at 50% 80%, rgba(245, 158, 11, 0.08) 0%, transparent 60%);
    pointer-events: none;
    animation: heroDrift 20s ease-in-out infinite alternate;
}
@keyframes heroDrift {
    0% { transform: translate3d(0, 0, 0) scale(1); }
    50% { transform: translate3d(1.5%, 1%, 0) scale(1.02); }
    100% { transform: translate3d(-1%, -0.5%, 0) scale(1.01); }
}
.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}
.hero h1 {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 6vw, var(--font-size-5xl));
    font-weight: 400;
    line-height: var(--line-height-tight);
    color: #ffffff;
    margin-bottom: var(--space-md);
    letter-spacing: -0.01em;
}
.hero-highlight {
    background: linear-gradient(120deg, #fbbf24, #f59e0b, #fbbf24);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}
.hero-subtitle {
    font-size: clamp(1rem, 1.8vw, 1.2rem);
    color: rgba(255, 255, 255, 0.8);
    max-width: 620px;
    margin: 0 auto var(--space-lg);
    line-height: 1.7;
}
.hero-categories {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    justify-content: center;
    margin-bottom: var(--space-xl);
}
.hero-categories span {
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.15);
    color: rgba(255, 255, 255, 0.9);
    padding: 6px 14px;
    border-radius: var(--radius-full);
    font-size: var(--font-size-sm);
    font-weight: 500;
    backdrop-filter: blur(4px);
}
.btn-cta {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 28px;
    background: var(--color-accent);
    color: #1a1a1a;
    font-weight: 700;
    font-size: var(--font-size-base);
    border-radius: var(--radius-full);
    text-decoration: none;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
    box-shadow: 0 4px 20px rgba(245, 158, 11, 0.4);
}
.btn-cta:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(245, 158, 11, 0.5);
    background: var(--color-accent-hover);
    text-decoration: none;
}

/* ---------- Main Layout ---------- */
.main-layout {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--space-lg);
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-lg);
}
@media (min-width: 1100px) {
    .main-layout {
        grid-template-columns: var(--sidebar-width) minmax(0, 1fr) var(--sidebar-width);
    }
}
.center-content {
    min-width: 0;
}

/* ---------- Sidebar Ads ---------- */
.sidebar-ad {
    display: none;
}
@media (min-width: 1100px) {
    .sidebar-ad {
        display: block;
        position: sticky;
        top: calc(var(--header-height) + 20px);
        align-self: start;
        max-height: calc(100vh - var(--header-height) - 40px);
        overflow: hidden;
    }
}
.ad-container {
    width: 100%;
    min-height: 600px;
    background: var(--color-surface);
    border: 1px dashed var(--color-border);
    border-radius: var(--radius-md);
    display: grid;
    place-items: center;
    color: var(--color-text-muted);
    font-size: var(--font-size-xs);
    overflow: hidden;
}

/* ---------- Banner Ads ---------- */
.ad-banner {
    width: 100%;
    min-height: 100px;
    background: var(--color-surface);
    border: 1px dashed var(--color-border);
    border-radius: var(--radius-md);
    display: grid;
    place-items: center;
    color: var(--color-text-muted);
    font-size: var(--font-size-xs);
    margin-bottom: var(--space-lg);
    overflow: hidden;
}
@media (min-width: 1100px) {
    .ad-banner--top,
    .ad-banner--footer {
        display: none;
    }
}

/* ---------- Converter Card ---------- */
.converter-card {
    background: var(--color-surface);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--space-lg) var(--space-xl);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--space-lg);
}
@media (max-width: 600px) {
    .converter-card {
        padding: var(--space-md);
    }
}

/* ---------- Category Tabs ---------- */
.category-tabs-wrapper {
    position: relative;
    margin-bottom: var(--space-md);
}
.category-tabs-wrapper::after {
    content: '';
    position: absolute;
    right: 0;
    top: 0;
    bottom: 0;
    width: 40px;
    background: linear-gradient(to right, transparent, var(--color-surface));
    pointer-events: none;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    z-index: 2;
}
[data-theme="dark"] .category-tabs-wrapper::after {
    background: linear-gradient(to right, transparent, var(--color-surface));
}
.category-tabs {
    display: flex;
    gap: 6px;
    overflow-x: auto;
    scroll-snap-type: x proximity;
    padding: 4px 44px 12px 4px;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
    scrollbar-color: var(--color-border) transparent;
}
.category-tabs::-webkit-scrollbar {
    height: 5px;
}
.category-tabs::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: var(--radius-full);
}
.cat-tab {
    flex: 0 0 auto;
    scroll-snap-align: start;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 9px 15px;
    border-radius: var(--radius-full);
    border: var(--border-width) solid var(--color-border);
    background: var(--color-surface);
    color: var(--color-text-secondary);
    font-weight: 600;
    font-size: var(--font-size-sm);
    white-space: nowrap;
    cursor: pointer;
    transition: all var(--transition-fast);
    min-height: 42px;
}
.cat-tab:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
    border-color: var(--color-primary);
}
.cat-tab.active {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    color: #fff;
    border-color: transparent;
    box-shadow: 0 4px 14px rgba(26, 115, 232, 0.3);
}
.cat-emoji {
    font-size: 1rem;
}
.category-description {
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
    margin-bottom: var(--space-lg);
    padding: 0 4px;
}

/* ---------- Converter Form ---------- */
.converter-form {
    display: grid;
    gap: var(--space-md);
    grid-template-columns: 1fr;
    align-items: end;
    margin-bottom: var(--space-lg);
}
@media (min-width: 600px) {
    .converter-form {
        grid-template-columns: 1fr 52px 1fr;
    }
}
.field-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.field-label {
    font-weight: 700;
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.04em;
}
.value-input {
    width: 100%;
    padding: 16px 18px;
    font-size: clamp(1.4rem, 2.5vw, 2rem);
    font-weight: 700;
    background: var(--color-surface);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    min-height: 56px;
}
.value-input:focus {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-glow);
}
.value-output {
    background: var(--color-bg);
    color: var(--color-primary);
    cursor: default;
}
.unit-selector {
    display: flex;
    gap: 6px;
}
.unit-select {
    flex: 1;
    padding: 12px 14px;
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    color: var(--color-text);
    font-weight: 600;
    font-size: var(--font-size-base);
    min-height: 48px;
    cursor: pointer;
    transition: border-color var(--transition-fast);
}
.unit-select:hover {
    border-color: var(--color-border-focus);
}
.unit-select:focus {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-glow);
}
.unit-select optgroup {
    font-weight: 700;
    color: var(--color-text-muted);
}
.unit-select option {
    font-weight: 500;
    color: var(--color-text);
    padding: 8px;
}
.star-btn {
    width: 48px;
    min-height: 48px;
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    font-size: 1.2rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: grid;
    place-items: center;
    color: var(--color-text-muted);
    flex-shrink: 0;
}
.star-btn:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
}
.star-btn[aria-pressed="true"] {
    background: var(--color-accent-light);
    border-color: var(--color-accent);
    color: var(--color-accent);
}

/* ---------- Swap Button ---------- */
.swap-button {
    width: 52px;
    height: 52px;
    border-radius: var(--radius-full);
    border: var(--border-width) solid var(--color-border);
    background: var(--color-surface);
    font-size: 1.4rem;
    cursor: pointer;
    display: grid;
    place-items: center;
    transition: all var(--transition-normal);
    color: var(--color-primary);
    justify-self: center;
    flex-shrink: 0;
}
.swap-button:hover {
    background: var(--color-primary-light);
    border-color: var(--color-primary);
}
.swap-button.rotated {
    transform: rotate(180deg);
}
@media (max-width: 599px) {
    .swap-button {
        transform: rotate(90deg);
    }
    .swap-button.rotated {
        transform: rotate(270deg);
    }
}

/* ---------- Action Buttons ---------- */
.action-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: var(--space-lg);
}
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 20px;
    border-radius: var(--radius-md);
    font-weight: 700;
    font-size: var(--font-size-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    min-height: 44px;
    border: var(--border-width) solid transparent;
    white-space: nowrap;
}
.btn:hover {
    transform: translateY(-1px);
}
.btn:active {
    transform: translateY(0);
}
.btn-primary {
    background: var(--color-accent);
    color: #1a1a1a;
    border-color: var(--color-accent);
    box-shadow: 0 2px 10px rgba(245, 158, 11, 0.25);
}
.btn-primary:hover {
    background: var(--color-accent-hover);
    box-shadow: 0 4px 16px rgba(245, 158, 11, 0.35);
}
.btn-secondary {
    background: var(--color-surface);
    color: var(--color-primary);
    border-color: var(--color-border);
}
.btn-secondary:hover {
    background: var(--color-primary-light);
    border-color: var(--color-primary);
}
.btn-small {
    padding: 8px 14px;
    font-size: var(--font-size-xs);
}

/* ---------- Formula Display ---------- */
.formula-display {
    padding: 14px 18px;
    background: var(--color-bg);
    border: 1px dashed var(--color-border);
    border-radius: var(--radius-md);
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    margin-bottom: var(--space-lg);
    min-height: 48px;
    display: flex;
    align-items: center;
}

/* ---------- Reference Table ---------- */
.reference-section {
    border-top: var(--border-width) solid var(--color-border);
    padding-top: var(--space-lg);
}
.reference-header {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-md);
}
.reference-header h3 {
    font-size: var(--font-size-base);
    color: var(--color-text);
    margin: 0;
}
.ref-search-input {
    padding: 10px 14px;
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-sm);
    background: var(--color-surface);
    color: var(--color-text);
    font-size: var(--font-size-sm);
    max-width: 220px;
    min-height: 40px;
}
.ref-search-input:focus {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-glow);
}
.reference-table-container {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-slow);
}
.reference-table-container.open {
    max-height: 2000px;
}
@media (min-width: 1100px) {
    .reference-table-container {
        max-height: 2000px;
    }
}
.reference-table {
    width: 100%;
    border-collapse: collapse;
    font-size: var(--font-size-sm);
}
.reference-table th {
    text-align: left;
    padding: 12px 14px;
    background: var(--color-bg);
    color: var(--color-text-secondary);
    font-weight: 700;
    font-size: var(--font-size-xs);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    border-bottom: 2px solid var(--color-border);
    position: sticky;
    top: 0;
}
.reference-table td {
    padding: 10px 14px;
    border-bottom: 1px solid var(--color-border);
    color: var(--color-text);
}
.reference-table tbody tr:hover {
    background: var(--color-surface-hover);
}
.reference-table tbody tr.active-row {
    background: var(--color-accent-light);
}
[data-theme="dark"] .reference-table tbody tr.active-row {
    background: rgba(245, 158, 11, 0.12);
}
.reference-table tbody tr td:last-child {
    font-weight: 700;
    color: var(--color-primary);
}

/* ---------- Recent Conversions ---------- */
.recent-card {
    background: var(--color-surface);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    box-shadow: var(--shadow-sm);
    margin-bottom: var(--space-lg);
}
.recent-card h3 {
    font-size: var(--font-size-base);
    margin-bottom: var(--space-md);
    color: var(--color-text);
}
.recent-list {
    display: grid;
    gap: 8px;
}
.recent-empty {
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
    text-align: center;
    padding: var(--space-md);
}
.recent-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 16px;
    background: var(--color-bg);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: var(--font-size-sm);
    transition: all var(--transition-fast);
    width: 100%;
    text-align: left;
    color: var(--color-text);
}
.recent-item:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
}
.recent-item .recent-arrow {
    color: var(--color-text-muted);
}

/* ---------- Features Card ---------- */
.features-card {
    background: var(--color-surface);
    border: var(--border-width) solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    box-shadow: var(--shadow-sm);
}
.features-card h3 {
    font-size: var(--font-size-xl);
    font-family: var(--font-display);
    margin-bottom: var(--space-lg);
    color: var(--color-text);
    text-align: center;
}
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(170px, 1fr));
    gap: var(--space-md);
}
.feature-item {
    text-align: center;
    padding: var(--space-md);
    border-radius: var(--radius-md);
    transition: background var(--transition-fast);
}
.feature-item:hover {
    background: var(--color-bg);
}
.feature-icon {
    font-size: 2rem;
    display: block;
    margin-bottom: var(--space-sm);
}
.feature-item h4 {
    font-size: var(--font-size-sm);
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: 4px;
}
.feature-item p {
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
    line-height: 1.5;
}

/* ---------- Footer ---------- */
.site-footer {
    background: var(--color-surface);
    border-top: var(--border-width) solid var(--color-border);
    padding: var(--space-2xl) 0;
    margin-top: var(--space-xl);
}
.footer-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-lg);
}
.footer-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-xl);
    margin-bottom: var(--space-lg);
}
@media (min-width: 700px) {
    .footer-grid {
        grid-template-columns: 2fr 1fr 1fr;
    }
}
.footer-brand p {
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
    margin-top: var(--space-sm);
    max-width: 260px;
}
.footer-col h4 {
    font-size: var(--font-size-xs);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
    font-weight: 700;
}
.footer-col ul {
    display: grid;
    gap: 6px;
}
.footer-col a {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}
.footer-col a:hover {
    color: var(--color-primary);
}
.footer-bottom {
    padding-top: var(--space-md);
    border-top: 1px solid var(--color-border);
    text-align: center;
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
}

/* ---------- Toast Notification ---------- */
.toast {
    position: fixed;
    bottom: -60px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--color-text);
    color: var(--color-bg);
    padding: 12px 24px;
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: var(--font-size-sm);
    z-index: 1000;
    box-shadow: var(--shadow-lg);
    transition: bottom var(--transition-normal);
    max-width: 90vw;
    text-align: center;
}
.toast.show {
    bottom: 24px;
}

/* ---------- Responsive Navigation ---------- */
@media (max-width: 768px) {
    .mobile-menu-btn {
        display: flex;
    }
    .main-nav {
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        bottom: 0;
        background: var(--color-surface);
        flex-direction: column;
        align-items: stretch;
        padding: var(--space-lg);
        gap: 4px;
        transform: translateX(100%);
        opacity: 0;
        transition: transform var(--transition-normal), opacity var(--transition-normal);
        z-index: 99;
        overflow-y: auto;
    }
    .main-nav.open {
        transform: translateX(0);
        opacity: 1;
    }
    .main-nav .nav-link {
        padding: 14px 16px;
        font-size: var(--font-size-base);
        border-radius: var(--radius-md);
    }
    .main-nav .theme-toggle-btn {
        align-self: flex-start;
        margin-top: var(--space-md);
    }
}

/* ---------- Reduced Motion ---------- */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    html { scroll-behavior: auto; }
}

/* ---------- Print Styles ---------- */
@media print {
    .site-header,
    .site-footer,
    .sidebar-ad,
    .ad-banner,
    .hero,
    .action-buttons,
    .recent-card,
    .features-card,
    .category-tabs-wrapper { display: none; }
    .converter-card { box-shadow: none; border: 1px solid #ccc; }
}