* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s, color 0.3s, transform 0.3s;
}

:root {
    --bg-color: #f8f9fa;
    --text-color: #333;
    --header-bg: #fff;
    --header-shadow: 0 2px 10px rgba(0,0,0,0.1);
    --card-bg: #fff;
    --card-hover: #f8f9fa;
    --border-color: #ddd;
    --primary-color: #3498db;
    --primary-hover: #2980b9;
    --feature-bg: #f8f9fa;
    --footer-bg: #2c3e50;
    --footer-text: #ecf0f1;
    --footer-link-hover: #3498db;
    --footer-border: #34495e;
    --section-bg: #fff;
    --input-bg: #fff;
    --input-border: #ddd;
    --results-bg: #e8f4fc;
    --accent-color: #e74c3c;
    --accent-hover: #c0392b;
}

.dark-theme {
    --bg-color: #141414;
    --text-color: #e0e0e0;
    --header-bg: #1a1a1a;
    --header-shadow: 0 2px 10px rgba(0,0,0,0.3);
    --card-bg: #2d2d2d;
    --card-hover: #3a3a3a;
    --border-color: #444;
    --primary-color: #58a6ff;
    --primary-hover: #6ea8fe;
    --feature-bg: #1a1a1a;
    --footer-bg: #121212;
    --footer-text: #b0b0b0;
    --footer-link-hover: #58a6ff;
    --footer-border: #333;
    --section-bg: #1a1a1a;
    --input-bg: #2d2d2d;
    --input-border: #555;
    --results-bg: #2a4461;
    --accent-color: #e74c3c;
    --accent-hover: #c0392b;
}

body {
    font-family: 'Roboto', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    min-height: 100vh;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

header {
    background-color: var(--header-bg);
    box-shadow: var(--header-shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 0;
}

.header-right {
    display: flex;
    align-items: center;
    gap: 15px;
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: #2c3e50;
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 5px;
}

.logo span {
    color: var(--primary-color);
}

.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.3s;
    position: relative;
}

.theme-toggle:hover {
    background-color: rgba(128, 128, 128, 0.2);
}

.theme-toggle::before {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 125%;
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--card-bg);
    color: var(--text-color);
    padding: 5px 10px;
    border-radius: 5px;
    font-size: 14px;
    white-space: nowrap;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s;
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
    z-index: 1000;
}

.theme-toggle:hover::before {
    opacity: 1;
    visibility: visible;
}

#theme-icon {
    width: 20px;
    height: 20px;
    color: var(--text-color);
}

nav ul {
    display: flex;
    list-style: none;
}

nav ul li {
    margin-left: 30px;
}

nav ul li a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: color 0.3s;
    position: relative;
}

nav ul li a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: width 0.3s;
}

nav ul li a:hover::after {
    width: 100%;
}

nav ul li a:hover {
    color: var(--primary-color);
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--text-color);
    position: relative;
}

.mobile-menu-btn::before {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 125%;
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--card-bg);
    color: var(--text-color);
    padding: 5px 10px;
    border-radius: 5px;
    font-size: 14px;
    white-space: nowrap;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s;
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
    z-index: 1000;
}

.mobile-menu-btn:hover::before {
    opacity: 1;
    visibility: visible;
}

.hero {
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.9) 0%, rgba(46, 204, 113, 0.8) 100%), url('../img/hero-bg.jpg') no-repeat center center/cover;
    color: white;
    text-align: center;
    padding: 120px 0;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(circle at center, rgba(0,0,0,0.3) 0%, rgba(0,0,0,0.7) 100%);
    z-index: 1;
}

.hero-content {
    position: relative;
    z-index: 2;
}

.hero h1 {
    font-size: 48px;
    margin-bottom: 20px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.5);
}

.hero p {
    font-size: 20px;
    margin-bottom: 30px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.btn {
    display: inline-block;
    background-color: var(--accent-color);
    color: white;
    padding: 12px 30px;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s;
    border: 2px solid var(--accent-color);
    box-shadow: 0 4px 15px rgba(231, 76, 60, 0.3);
}

.btn:hover {
    background-color: transparent;
    color: var(--accent-color);
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(231, 76, 60, 0.4);
}

.btn-primary {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
}

.btn-primary:hover {
    background-color: transparent;
    color: var(--primary-color);
    box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
}

.features {
    padding: 100px 0;
    background-color: var(--section-bg);
}

.section-title {
    text-align: center;
    font-size: 36px;
    margin-bottom: 60px;
    color: var(--text-color);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -15px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background-color: var(--primary-color);
    border-radius: 2px;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.feature-card {
    background-color: var(--card-bg);
    border-radius: 15px;
    padding: 30px;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
    border: 1px solid var(--border-color);
    position: relative;
    overflow: hidden;
    z-index: 1;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 5px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.3s;
    z-index: -1;
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.15);
}

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

.feature-icon {
    font-size: 60px;
    color: var(--primary-color);
    margin-bottom: 20px;
    display: inline-block;
}

.feature-card h3 {
    margin-bottom: 15px;
    color: var(--text-color);
    font-size: 22px;
}

.feature-card p {
    color: #666;
}

.products {
    padding: 100px 0;
    background-color: var(--feature-bg);
}

.products-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
}

.product-card {
    background-color: var(--card-bg);
    border-radius: 15px;
    overflow: hidden;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
    border: 1px solid var(--border-color);
    position: relative;
}

.product-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.15);
}

.product-image {
    height: 200px;
    overflow: hidden;
    position: relative;
}

.product-image::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(transparent, rgba(0,0,0,0.3));
    opacity: 0;
    transition: opacity 0.3s;
}

.product-card:hover .product-image::after {
    opacity: 1;
}

.product-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s;
}

.product-card:hover .product-image img {
    transform: scale(1.1);
}

.product-info {
    padding: 25px;
}

.product-info h3 {
    margin-bottom: 10px;
    color: #2c3e50;
    font-size: 20px;
}

.product-price {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.product-description {
    color: #666;
    margin-bottom: 20px;
    font-size: 14px;
    line-height: 1.5;
}

.calculator {
    padding: 100px 0;
    background-color: var(--section-bg);
}

.calculator-container {
    max-width: 800px;
    margin: 0 auto;
    background-color: var(--card-bg);
    border-radius: 15px;
    padding: 50px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    border: 1px solid var(--border-color);
}

.calculator h2 {
    text-align: center;
    margin-bottom: 40px;
    color: #2c3e50;
    font-size: 32px;
}

.form-group {
    margin-bottom: 25px;
}

.form-group label {
    display: block;
    margin-bottom: 10px;
    font-weight: 500;
    color: var(--text-color);
    font-size: 16px;
}

.form-control {
    width: 100%;
    padding: 14px 18px;
    border: 2px solid var(--input-border);
    border-radius: 10px;
    font-size: 16px;
    background-color: var(--input-bg);
    color: var(--text-color);
    transition: border-color 0.3s, box-shadow 0.3s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.form-row {
    display: flex;
    gap: 20px;
}

.form-row .form-group {
    flex: 1;
}

.btn-calculate {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 15px 35px;
    border-radius: 50px;
    cursor: pointer;
    font-size: 18px;
    font-weight: 500;
    width: 100%;
    margin-top: 30px;
    transition: all 0.3s;
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
    border: 2px solid var(--primary-color);
}

.btn-calculate:hover {
    background-color: transparent;
    color: var(--primary-color);
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
}

.results {
    margin-top: 40px;
    padding: 30px;
    background-color: var(--results-bg);
    border-radius: 10px;
    display: none;
    border: 2px solid var(--border-color);
    animation: fadeIn 0.5s ease-in;
}

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

.results h3 {
    margin-bottom: 20px;
    color: var(--text-color);
    font-size: 22px;
}

.result-item {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
    font-size: 16px;
}

.total {
    font-weight: 700;
    font-size: 22px;
    color: var(--primary-color);
    margin-top: 20px;
    padding-top: 20px;
    border-top: 3px solid var(--border-color);
}

.catalog {
    padding: 100px 0;
    background-color: var(--feature-bg);
}

.catalog-tabs {
    display: flex;
    justify-content: center;
    margin-bottom: 40px;
    border-bottom: 2px solid var(--border-color);
    position: relative;
}

.catalog-tabs::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 100%;
    height: 1px;
    background-color: var(--border-color);
}

.catalog-tab {
    padding: 15px 30px;
    background: none;
    border: none;
    font-size: 18px;
    font-weight: 500;
    cursor: pointer;
    border-bottom: 3px solid transparent;
    transition: all 0.3s;
    color: var(--text-color);
    position: relative;
    z-index: 1;
}

.catalog-tab:hover {
    color: var(--primary-color);
}

.catalog-tab.active {
    border-bottom: 3px solid var(--primary-color);
    color: var(--primary-color);
    z-index: 2;
}

.catalog-content {
    display: none;
}

.catalog-content.active {
    display: block;
}

.catalog-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 25px;
}

.catalog-item {
    text-align: center;
    position: relative;
    overflow: hidden;
    border-radius: 10px;
}

.catalog-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(transparent, rgba(0,0,0,0.5));
    opacity: 0;
    transition: opacity 0.3s;
    z-index: 1;
}

.catalog-item:hover::before {
    opacity: 1;
}

.catalog-item img {
    width: 100%;
    height: 150px;
    object-fit: cover;
    border-radius: 10px;
    transition: transform 0.5s;
    z-index: 0;
}

.catalog-item:hover img {
    transform: scale(1.1);
}

.catalog-item p {
    font-size: 14px;
    color: var(--text-color);
    margin-top: 10px;
    font-weight: 500;
}

footer {
    background-color: var(--footer-bg);
    color: var(--footer-text);
    padding: 80px 0 40px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
    margin-bottom: 60px;
}

.footer-column h3 {
    font-size: 20px;
    margin-bottom: 25px;
    color: var(--primary-color);
    position: relative;
    padding-bottom: 10px;
}

.footer-column h3::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 50px;
    height: 2px;
    background-color: var(--primary-color);
}

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

.footer-column ul li {
    margin-bottom: 15px;
}

.footer-column ul li a {
    color: var(--footer-text);
    text-decoration: none;
    transition: color 0.3s, padding-left 0.3s;
    display: flex;
    align-items: center;
    gap: 10px;
}

.footer-column ul li a:hover {
    color: var(--footer-link-hover);
    padding-left: 10px;
}

.footer-column p, .footer-column a {
    color: var(--footer-text);
    margin-bottom: 15px;
    display: block;
    text-decoration: none;
    transition: color 0.3s;
}

.footer-column a:hover {
    color: var(--footer-link-hover);
}

.social-links {
    display: flex;
    gap: 15px;
    margin-top: 20px;
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background-color: rgba(255,255,255,0.1);
    border-radius: 50%;
    color: var(--footer-text);
    text-decoration: none;
    transition: all 0.3s;
}

.social-link:hover {
    background-color: var(--primary-color);
    transform: translateY(-3px);
}

.footer-bottom {
    text-align: center;
    padding-top: 40px;
    border-top: 1px solid var(--footer-border);
    font-size: 14px;
    color: #bdc3c7;
}

.page {
    display: none;
    padding: 80px 0;
}

.page.active {
    display: block;
}

@media (max-width: 992px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .hero h1 {
        font-size: 40px;
    }
    
    .hero p {
        font-size: 18px;
    }
}

@media (max-width: 768px) {
    .mobile-menu-btn {
        display: block;
    }
    
    .header-right {
        gap: 10px;
    }
    
    nav ul {
        display: none;
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background-color: var(--header-bg);
        flex-direction: column;
        padding: 20px 0;
        box-shadow: 0 5px 10px rgba(0,0,0,0.1);
        border-bottom: 1px solid var(--border-color);
        z-index: 100;
    }
    
    nav ul.show {
        display: flex;
    }
    
    nav ul li {
        margin: 10px 0;
        text-align: center;
    }
    
    .features-grid, .catalog-grid {
        grid-template-columns: 1fr;
    }
    
    .form-row {
        flex-direction: column;
    }
    
    .section-title {
        font-size: 30px;
    }
    
    .hero {
        padding: 100px 0;
    }
    
    .hero h1 {
        font-size: 32px;
    }
    
    .calculator-container {
        padding: 30px;
    }
    
    .btn {
        padding: 10px 25px;
        font-size: 16px;
    }
}