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

:root {
    --primary-color: #10b981;
    --secondary-color: #059669;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    --light-bg: #f3f4f6;
    --dark-text: #1f2937;
    --gray-text: #6b7280;
    --white: #ffffff;
    --border-color: #e5e7eb;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--light-bg);
    color: var(--dark-text);
    line-height: 1.6;
}

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

/* Header Styles */
header {
    background-color: var(--white);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    text-decoration: none;
}

.logo i {
    font-size: 2rem;
}

nav ul {
    display: flex;
    gap: 2rem;
    list-style: none;
}

nav a {
    color: var(--dark-text);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
    padding: 0.5rem 0;
}

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

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

/* Main Content */
main {
    min-height: calc(100vh - 200px);
    padding: 2rem 0;
}

.page-header {
    text-align: center;
    margin-bottom: 3rem;
}

.page-header h1 {
    font-size: 2.5rem;
    color: var(--dark-text);
    margin-bottom: 0.5rem;
}

.page-header p {
    font-size: 1.1rem;
    color: var(--gray-text);
}

/* Card Grid */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.card {
    background: var(--white);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    transition: transform 0.3s, box-shadow 0.3s;
    text-decoration: none;
    color: var(--dark-text);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.card-icon {
    width: 60px;
    height: 60px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    color: var(--white);
    margin-bottom: 1rem;
}

.card-icon.green {
    background-color: var(--primary-color);
}

.card-icon.blue {
    background-color: var(--info-color);
}

.card-icon.orange {
    background-color: var(--warning-color);
}

.card-icon.red {
    background-color: var(--danger-color);
}

.card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
    color: var(--dark-text);
}

.card p {
    color: var(--gray-text);
    font-size: 0.95rem;
}

/* Category Section */
.category-section {
    margin-bottom: 3rem;
}

.category-title {
    font-size: 1.8rem;
    color: var(--dark-text);
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid var(--primary-color);
    display: inline-block;
}

/* Calculator Container */
.calculator-container {
    background: var(--white);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 3rem;
}

.calculator-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

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

.form-group input,
.form-group select,
.form-group textarea {
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

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

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s, transform 0.1s;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background-color: var(--primary-color);
    color: var(--white);
}

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

.btn-secondary {
    background-color: var(--gray-text);
    color: var(--white);
}

.btn-secondary:hover {
    background-color: #4b5563;
}

.result-box {
    background-color: #ecfdf5;
    border: 2px solid var(--primary-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-top: 1rem;
}

.result-box h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.result-value {
    font-size: 2rem;
    font-weight: bold;
    color: var(--dark-text);
}

/* Calculator Display */
.calculator-display {
    background-color: #1f2937;
    color: var(--white);
    padding: 1.5rem;
    border-radius: 8px;
    text-align: right;
    font-size: 2rem;
    margin-bottom: 1rem;
    min-height: 80px;
    word-wrap: break-word;
}

.calculator-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.75rem;
}

.calc-btn {
    padding: 1.5rem;
    font-size: 1.2rem;
    font-weight: 600;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
}

.calc-btn:active {
    transform: scale(0.95);
}

.calc-btn.number {
    background-color: var(--white);
    color: var(--dark-text);
    border: 2px solid var(--border-color);
}

.calc-btn.number:hover {
    background-color: var(--light-bg);
}

.calc-btn.operator {
    background-color: var(--primary-color);
    color: var(--white);
}

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

.calc-btn.clear {
    background-color: var(--danger-color);
    color: var(--white);
}

.calc-btn.clear:hover {
    background-color: #dc2626;
}

.calc-btn.equals {
    background-color: var(--info-color);
    color: var(--white);
}

.calc-btn.equals:hover {
    background-color: #2563eb;
}

/* Info Section */
.info-section {
    background: var(--white);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.info-section h2 {
    color: var(--dark-text);
    margin-bottom: 1rem;
    font-size: 1.8rem;
}

.info-section h3 {
    color: var(--dark-text);
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    font-size: 1.3rem;
}

.info-section p {
    color: var(--gray-text);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.info-section ul {
    margin-left: 2rem;
    margin-bottom: 1rem;
}

.info-section li {
    color: var(--gray-text);
    margin-bottom: 0.5rem;
}

/* Footer */
footer {
    background-color: var(--dark-text);
    color: var(--white);
    padding: 2rem 0;
    margin-top: 4rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

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

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: #d1d5db;
    text-decoration: none;
    transition: color 0.3s;
}

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

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid #374151;
    color: #9ca3af;
}

/* Sitemap */
.sitemap-list {
    list-style: none;
}

.sitemap-list > li {
    margin-bottom: 2rem;
}

.sitemap-list > li > a {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-color);
    text-decoration: none;
}

.sitemap-list > li > a:hover {
    text-decoration: underline;
}

.sitemap-list ul {
    margin-left: 2rem;
    margin-top: 0.5rem;
    list-style: none;
}

.sitemap-list ul li {
    margin-bottom: 0.5rem;
}

.sitemap-list ul a {
    color: var(--dark-text);
    text-decoration: none;
}

.sitemap-list ul a:hover {
    color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .header-content {
        position: relative;
    }

    .mobile-menu-btn {
        display: block;
    }

    nav {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--white);
        box-shadow: var(--shadow);
        display: none;
    }

    nav.active {
        display: block;
    }

    nav ul {
        flex-direction: column;
        gap: 0;
        padding: 1rem 0;
    }

    nav a {
        display: block;
        padding: 1rem 20px;
    }

    .page-header h1 {
        font-size: 2rem;
    }

    .card-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .calculator-buttons {
        gap: 0.5rem;
    }

    .calc-btn {
        padding: 1.2rem;
        font-size: 1rem;
    }

    .calculator-display {
        font-size: 1.5rem;
        padding: 1rem;
    }

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

@media (max-width: 480px) {
    .page-header h1 {
        font-size: 1.5rem;
    }

    .page-header p {
        font-size: 1rem;
    }

    .calculator-container {
        padding: 1rem;
    }

    .result-value {
        font-size: 1.5rem;
    }
}