/* ================================
   CalcHub - Modern Calculator Platform
   Beautiful, Ergonomic, User-Friendly Design
   ================================ */

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

:root {
    /* Primary Colors */
    --primary-500: #6366f1;
    --primary-600: #4f46e5;
    --primary-700: #4338ca;

    /* Accent Colors */
    --accent-500: #06b6d4;
    --accent-600: #0891b2;

    /* Success/Error */
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;

    /* Light Theme */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --bg-card: #ffffff;

    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;

    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1);

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

    /* Transitions */
    --transition: all 0.2s ease-in-out;
}

/* Dark Theme */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --bg-card: #1e293b;

    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;

    --border-color: #334155;
    --border-hover: #475569;
}

/* === Base Styles === */
html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

/* === Header === */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-lg) 0;
}

.nav-brand .logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary-600);
    text-decoration: none;
}

.logo-icon {
    width: 32px;
    height: 32px;
    color: var(--primary-600);
}

.logo-text {
    background: linear-gradient(135deg, var(--primary-600), var(--accent-600));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Theme Toggle */
.theme-toggle {
    width: 40px;
    height: 40px;
    border: none;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.theme-toggle:hover {
    background: var(--bg-tertiary);
    transform: scale(1.05);
}

.theme-toggle svg {
    width: 20px;
    height: 20px;
    color: var(--text-primary);
}

.moon-icon {
    display: none;
}

[data-theme="dark"] .sun-icon {
    display: none;
}

[data-theme="dark"] .moon-icon {
    display: block;
}

/* === Hero Section === */
.hero {
    padding: var(--space-3xl) 0;
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
}

.gradient-text {
    background: linear-gradient(135deg, var(--primary-600), var(--accent-600));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-2xl);
    line-height: 1.6;
}

/* === Search Bar === */
.search-container {
    position: relative;
    max-width: 600px;
    margin: 0 auto var(--space-2xl);
}

.search-icon {
    position: absolute;
    left: var(--space-lg);
    top: 50%;
    transform: translateY(-50%);
    width: 20px;
    height: 20px;
    color: var(--text-muted);
    pointer-events: none;
}

.search-input {
    width: 100%;
    padding: var(--space-lg) var(--space-lg) var(--space-lg) 3.5rem;
    font-size: 1.125rem;
    font-family: var(--font-sans);
    color: var(--text-primary);
    background: var(--bg-card);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-xl);
    outline: none;
    transition: var(--transition);
    box-shadow: var(--shadow-lg);
}

.search-input:focus {
    border-color: var(--primary-500);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
}

.search-input::placeholder {
    color: var(--text-muted);
}

/* Stats */
.stats {
    display: flex;
    justify-content: center;
    gap: var(--space-2xl);
    margin-top: var(--space-2xl);
}

.stat-item {
    text-align: center;
}

.stat-number {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-600);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* === Category Filter === */
.category-filter {
    padding: var(--space-xl) 0;
    border-bottom: 1px solid var(--border-color);
}

.filter-pills {
    display: flex;
    gap: var(--space-sm);
    overflow-x: auto;
    padding-bottom: var(--space-sm);
    -webkit-overflow-scrolling: touch;
}

.filter-pills::-webkit-scrollbar {
    height: 4px;
}

.filter-pills::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 2px;
}

.filter-pill {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-lg);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

.filter-pill:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-hover);
}

.filter-pill.active {
    background: var(--primary-600);
    border-color: var(--primary-600);
    color: white;
}

.filter-pill .pill-icon {
    font-size: 2.6rem;
    line-height: 1;
}

.filter-pill .pill-label {
    font-size: 0.95rem;
    font-weight: 600;
    color: inherit;
}

/* === Calculators Section === */
.calculators-section {
    padding: var(--space-3xl) 0;
}

.category-group {
    margin-bottom: var(--space-3xl);
}

.category-group.hidden {
    display: none;
}

.category-header {
    margin-bottom: var(--space-2xl);
}

.category-title {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--space-sm);
}

.category-icon {
    font-size: 4rem;
}

.category-description {
    color: var(--text-secondary);
    font-size: 1.125rem;
}

/* === Calculator Cards Grid === */
.calculators-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--space-xl);
}

.calculator-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.calculator-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-600), var(--accent-600));
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.3s ease;
}

.calculator-card:hover::before {
    transform: scaleX(1);
}

.calculator-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-500);
}

.card-icon-wrapper {
    margin-bottom: var(--space-lg);
}

.card-icon {
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    background: linear-gradient(135deg, var(--primary-500), var(--accent-500));
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--space-sm);
}

.card-description {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: var(--space-lg);
}

.card-tags {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

.tag {
    padding: 0.25rem 0.75rem;
    background: var(--bg-secondary);
    color: var(--text-secondary);
    font-size: 0.75rem;
    font-weight: 500;
    border-radius: var(--radius-md);
}

.tag.popular {
    background: var(--primary-100);
    color: var(--primary-700);
}

[data-theme="dark"] .tag.popular {
    background: rgba(99, 102, 241, 0.2);
    color: var(--primary-400);
}

/* === Features Section === */
.features-section {
    padding: var(--space-3xl) 0;
    background: var(--bg-secondary);
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--space-2xl);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--space-xl);
}

.feature-card {
    text-align: center;
    padding: var(--space-xl);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: var(--space-md);
}

.feature-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--space-sm);
}

.feature-description {
    color: var(--text-secondary);
}

/* === Footer === */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--space-3xl) 0 var(--space-xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--space-2xl);
    margin-bottom: var(--space-2xl);
}

.footer-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-600);
    margin-bottom: var(--space-sm);
}

.footer-text {
    color: var(--text-secondary);
    line-height: 1.6;
}

.footer-heading {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--space-md);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--space-sm);
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
}

.footer-links a:hover {
    color: var(--primary-600);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--space-xl);
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* === Responsive Design === */
@media (max-width: 768px) {
    .container {
        padding: 0 var(--space-md);
    }
    .nav {
        padding: var(--space-md) 0;
    }
    .hero {
        padding: var(--space-2xl) 0;
    }
    .hero-title {
        font-size: 2.4rem;
    }
    .hero-subtitle {
        font-size: 1.1rem;
    }
    .stats {
        gap: var(--space-lg);
    }
    .stat-number {
        font-size: 1.5rem;
    }
    .calculators-grid {
        grid-template-columns: 1fr;
    }
    .features-grid {
        grid-template-columns: 1fr;
    }
    .category-title {
        font-size: 1.5rem;
    }
}

@media (max-width: 540px) {
    .container {
        padding: 0 var(--space-sm);
    }
    .hero-title {
        font-size: 2rem;
    }
    .hero-subtitle {
        font-size: 1rem;
    }
    .stats {
        flex-direction: column;
        align-items: stretch;
    }
    .stats .stat-item {
        width: 100%;
    }
    .nav {
        flex-wrap: wrap;
        row-gap: var(--space-sm);
    }
}

/* === Animations === */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.calculator-card {
    animation: fadeIn 0.5s ease-out backwards;
}

.calculator-card:nth-child(1) { animation-delay: 0.1s; }
.calculator-card:nth-child(2) { animation-delay: 0.2s; }
.calculator-card:nth-child(3) { animation-delay: 0.3s; }
.calculator-card:nth-child(4) { animation-delay: 0.4s; }