/* ===== RESET & BASE STYLES ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Primary Colors */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --warm-gradient: linear-gradient(135deg, #fa709a 0%, #fee140 100%);

    /* Solid Colors */
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --accent-color: #f5576c;
    --success-color: #00f2fe;

    /* Neutral Colors */
    --text-dark: #2d3748;
    --text-medium: #4a5568;
    --text-light: #718096;
    --border-color: #e2e8f0;
    --bg-light: #f7fafc;
    --bg-white: #ffffff;

    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.15);

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

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

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    color: var(--text-dark);
    line-height: 1.6;
    background-color: var(--bg-light);
    overflow-x: hidden;
}

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

/* ===== HEADER ===== */
.header {
    background: var(--bg-white);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: var(--transition-base);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition-fast);
}

.logo i {
    font-size: 1.5rem;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo:hover {
    transform: translateY(-2px);
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-dark);
    cursor: pointer;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-md);
    align-items: center;
}

.nav-menu a {
    display: flex;
    align-items: center;
    gap: 0.375rem;
    color: var(--text-medium);
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-md);
    transition: var(--transition-fast);
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--primary-color);
    background: rgba(102, 126, 234, 0.1);
}

.nav-menu i {
    font-size: 0.875rem;
}

/* ===== HERO SECTION ===== */
.hero {
    background: var(--primary-gradient);
    color: white;
    padding: var(--spacing-xl) 0;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg width="100" height="100" xmlns="http://www.w3.org/2000/svg"><defs><pattern id="grid" width="100" height="100" patternUnits="userSpaceOnUse"><path d="M 100 0 L 0 0 0 100" fill="none" stroke="rgba(255,255,255,0.05)" stroke-width="1"/></pattern></defs><rect width="100%" height="100%" fill="url(%23grid)"/></svg>');
    opacity: 0.5;
}

.hero-content {
    position: relative;
    z-index: 1;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.hero h1 i {
    font-size: 3rem;
}

.hero-subtitle {
    font-size: 1.125rem;
    max-width: 800px;
    margin: 0 auto var(--spacing-lg);
    opacity: 0.95;
    line-height: 1.7;
}

.hero-features {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.feature-badge {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-lg);
    font-weight: 500;
}

.feature-badge i {
    font-size: 1.125rem;
}

/* ===== CALCULATOR SECTION ===== */
.calculator-section {
    padding: var(--spacing-xl) 0;
}

.calculator-card {
    background: var(--bg-white);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-lg);
    max-width: 900px;
    margin: 0 auto;
}

.calculator-header {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.calculator-header h2 {
    font-size: 2rem;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
}

.calculator-header h2 i {
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.calculator-header p {
    color: var(--text-light);
}

/* ===== CONVERSION TYPE SELECTOR ===== */
.conversion-type-selector {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.type-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.375rem;
    padding: var(--spacing-sm);
    background: var(--bg-light);
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition-fast);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-medium);
}

.type-btn i {
    font-size: 1.5rem;
}

.type-btn:hover {
    background: rgba(102, 126, 234, 0.1);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.type-btn.active {
    background: var(--primary-gradient);
    color: white;
    border-color: var(--primary-color);
}

/* ===== CONVERTER INTERFACE ===== */
.converter-interface {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: var(--spacing-md);
    align-items: center;
    margin-bottom: var(--spacing-lg);
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.input-group label {
    display: flex;
    align-items: center;
    gap: 0.375rem;
    font-weight: 600;
    color: var(--text-dark);
    font-size: 0.875rem;
}

.input-wrapper {
    display: flex;
    gap: var(--spacing-xs);
}

.input-wrapper input {
    flex: 1;
    padding: var(--spacing-sm);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: var(--transition-fast);
    background: var(--bg-white);
}

.input-wrapper input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.input-wrapper input[readonly] {
    background: var(--bg-light);
    cursor: not-allowed;
}

.unit-select {
    padding: var(--spacing-sm);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--bg-white);
    cursor: pointer;
    transition: var(--transition-fast);
    min-width: 120px;
}

.unit-select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.swap-button-wrapper {
    display: flex;
    align-items: center;
    justify-content: center;
}

.swap-btn {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--primary-gradient);
    border: none;
    color: white;
    font-size: 1.25rem;
    cursor: pointer;
    transition: var(--transition-fast);
    box-shadow: var(--shadow-md);
}

.swap-btn:hover {
    transform: rotate(180deg) scale(1.1);
    box-shadow: var(--shadow-lg);
}

/* ===== CALCULATOR ACTIONS ===== */
.calculator-actions {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
}

.btn-primary,
.btn-secondary {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition-fast);
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: var(--bg-light);
    color: var(--text-medium);
}

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

/* ===== RESULT INFO ===== */
.result-info {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-md);
    background: linear-gradient(135deg, #e0f2fe 0%, #dbeafe 100%);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--text-dark);
    font-weight: 500;
}

.result-info i {
    font-size: 1.25rem;
    color: var(--primary-color);
}

/* ===== RELATED CONVERTERS & FEATURES SECTIONS ===== */
.related-converters,
.features-section,
.articles-section {
    padding: var(--spacing-xl) 0;
}

.section-title {
    text-align: center;
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-dark);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
}

.section-title i {
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-subtitle {
    text-align: center;
    color: var(--text-light);
    max-width: 700px;
    margin: 0 auto var(--spacing-lg);
    font-size: 1.125rem;
}

/* ===== CONVERTERS GRID ===== */
.converters-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.converter-card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
    text-decoration: none;
    color: var(--text-dark);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.converter-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.converter-icon {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
    color: white;
    margin-bottom: var(--spacing-xs);
}

.converter-icon.temp {
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
}

.converter-icon.length {
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
}

.converter-icon.weight {
    background: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);
}

.converter-icon.speed {
    background: linear-gradient(135deg, #fa709a 0%, #fee140 100%);
}

.converter-icon.area {
    background: linear-gradient(135deg, #30cfd0 0%, #330867 100%);
}

.converter-icon.volume {
    background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%);
}

.converter-icon.time {
    background: linear-gradient(135deg, #ff9a9e 0%, #fecfef 100%);
}

.converter-icon.data {
    background: linear-gradient(135deg, #ffecd2 0%, #fcb69f 100%);
}

.converter-card h3 {
    font-size: 1.25rem;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.converter-card p {
    color: var(--text-medium);
    flex-grow: 1;
    line-height: 1.6;
}

.card-link {
    color: var(--primary-color);
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.375rem;
    transition: var(--transition-fast);
}

.converter-card:hover .card-link {
    gap: var(--spacing-sm);
}

/* ===== FEATURES GRID ===== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
}

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

.feature-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-md);
    border-radius: 50%;
    background: var(--primary-gradient);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

.feature-item:hover .feature-icon {
    transform: scale(1.1) rotate(5deg);
    box-shadow: var(--shadow-lg);
}

.feature-item h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
    color: var(--text-dark);
}

.feature-item p {
    color: var(--text-medium);
    line-height: 1.6;
}

/* ===== ARTICLES GRID ===== */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.article-card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

.article-card:hover {
    box-shadow: var(--shadow-xl);
    transform: translateY(-4px);
}

.article-icon {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    background: var(--secondary-gradient);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
    color: white;
    margin-bottom: var(--spacing-md);
}

.article-card h3 {
    margin-bottom: var(--spacing-sm);
}

.article-card h3 a {
    color: var(--text-dark);
    text-decoration: none;
    font-size: 1.125rem;
    transition: var(--transition-fast);
}

.article-card h3 a:hover {
    color: var(--primary-color);
}

.article-card p {
    color: var(--text-medium);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.read-more {
    display: inline-flex;
    align-items: center;
    gap: 0.375rem;
    color: var(--primary-color);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition-fast);
}

.read-more:hover {
    gap: var(--spacing-sm);
}

/* ===== FOOTER ===== */
.footer {
    background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%);
    color: #e2e8f0;
    padding: var(--spacing-xl) 0 var(--spacing-lg);
}

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

.footer-col h4 {
    color: white;
    margin-bottom: var(--spacing-md);
    font-size: 1.125rem;
}

.footer-col p {
    line-height: 1.7;
    margin-bottom: var(--spacing-md);
    color: #cbd5e0;
}

.footer-col ul {
    list-style: none;
}

.footer-col ul li {
    margin-bottom: var(--spacing-xs);
}

.footer-col ul li a {
    color: #cbd5e0;
    text-decoration: none;
    transition: var(--transition-fast);
}

.footer-col ul li a:hover {
    color: white;
    padding-left: var(--spacing-xs);
}

.social-links {
    display: flex;
    gap: var(--spacing-sm);
}

.social-links a {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    text-decoration: none;
    transition: var(--transition-fast);
}

.social-links a:hover {
    background: var(--primary-gradient);
    transform: translateY(-3px);
}

.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding-top: var(--spacing-md);
    text-align: center;
    color: #cbd5e0;
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 768px) {
    .mobile-menu-toggle {
        display: block;
    }

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-white);
        flex-direction: column;
        padding: var(--spacing-md);
        box-shadow: var(--shadow-lg);
        display: none;
    }

    .nav-menu.active {
        display: flex;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero h1 i {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .conversion-type-selector {
        grid-template-columns: repeat(4, 1fr);
    }

    .type-btn span {
        font-size: 0.75rem;
    }

    .converter-interface {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }

    .swap-button-wrapper {
        order: 2;
    }

    .swap-btn {
        transform: rotate(90deg);
    }

    .swap-btn:hover {
        transform: rotate(270deg) scale(1.1);
    }

    .calculator-actions {
        flex-direction: column;
    }

    .btn-primary,
    .btn-secondary {
        width: 100%;
        justify-content: center;
    }

    .converters-grid {
        grid-template-columns: 1fr;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .articles-grid {
        grid-template-columns: 1fr;
    }

    .footer-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .conversion-type-selector {
        grid-template-columns: repeat(2, 1fr);
    }

    .hero h1 {
        font-size: 1.5rem;
    }

    .section-title {
        font-size: 1.5rem;
    }
}