* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --accent-color: #3b82f6;
    --text-color: #1f2937;
    --light-gray: #f3f4f6;
    --border-color: #e5e7eb;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: #ffffff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 40px 0;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    font-weight: 700;
}

header .tagline {
    font-size: 1.1rem;
    opacity: 0.95;
}

.main-nav {
    background-color: white;
    border-bottom: 2px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
}

.main-nav ul {
    list-style: none;
    display: flex;
    gap: 30px;
    padding: 15px 0;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    padding: 8px 16px;
    border-radius: 5px;
    transition: all 0.3s ease;
}

.main-nav a:hover,
.main-nav a.active {
    background-color: var(--primary-color);
    color: white;
}

main {
    padding: 40px 20px;
}

.hero {
    text-align: center;
    margin-bottom: 50px;
    padding: 30px;
    background: var(--light-gray);
    border-radius: 10px;
}

.hero h2 {
    font-size: 2rem;
    margin-bottom: 15px;
    color: var(--primary-color);
}

.hero p {
    font-size: 1.2rem;
    color: #6b7280;
}

.categories {
    margin-bottom: 60px;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 30px;
}

.category-card {
    background: white;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    padding: 30px;
    transition: all 0.3s ease;
}

.category-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    border-color: var(--primary-color);
}

.category-card .icon {
    font-size: 3rem;
    margin-bottom: 15px;
}

.category-card h3 {
    font-size: 1.5rem;
    margin-bottom: 10px;
    color: var(--primary-color);
}

.category-card p {
    color: #6b7280;
    margin-bottom: 20px;
}

.tool-list {
    list-style: none;
    margin-top: 15px;
}

.tool-list li {
    margin-bottom: 8px;
}

.tool-list a {
    color: var(--text-color);
    text-decoration: none;
    display: block;
    padding: 8px 12px;
    border-radius: 5px;
    transition: all 0.2s ease;
}

.tool-list a:hover {
    background-color: var(--light-gray);
    color: var(--primary-color);
    padding-left: 20px;
}

.popular-tools {
    margin-top: 50px;
    padding: 40px;
    background: var(--light-gray);
    border-radius: 10px;
}

.popular-tools h2 {
    font-size: 1.8rem;
    margin-bottom: 25px;
    color: var(--primary-color);
    text-align: center;
}

.tool-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
}

.tool-link {
    display: block;
    padding: 15px 20px;
    background: white;
    color: var(--text-color);
    text-decoration: none;
    border-radius: 8px;
    text-align: center;
    font-weight: 500;
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.tool-link:hover {
    background-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.calculator-container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
}

.calculator-container h2 {
    color: var(--primary-color);
    margin-bottom: 20px;
    font-size: 2rem;
}

.calculator-form {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.form-group label {
    font-weight: 600;
    color: var(--text-color);
}

.form-group input,
.form-group select {
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 5px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.btn {
    padding: 12px 30px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(37, 99, 235, 0.3);
}

.btn:active {
    transform: translateY(0);
}

.result-box {
    margin-top: 30px;
    padding: 20px;
    background: var(--light-gray);
    border-left: 4px solid var(--success-color);
    border-radius: 5px;
}

.result-box h3 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.result-box .result-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--success-color);
}

.breadcrumb {
    padding: 15px 0;
    color: #6b7280;
}

.breadcrumb a {
    color: var(--primary-color);
    text-decoration: none;
}

.breadcrumb a:hover {
    text-decoration: underline;
}

footer {
    background-color: var(--text-color);
    color: white;
    text-align: center;
    padding: 30px 0;
    margin-top: 60px;
}

footer p {
    margin-bottom: 5px;
    opacity: 0.9;
}

@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .hero h2 {
        font-size: 1.5rem;
    }

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

    .main-nav ul {
        flex-direction: column;
        gap: 10px;
    }

    .calculator-container {
        padding: 20px;
    }
}