:root {
    --primary-color: #4a90e2;
    --secondary-color: #5cb85c;
    --dark-color: #2c3e50;
    --light-bg: #f8f9fa;
    --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --hover-shadow: 0 8px 15px rgba(0, 0, 0, 0.2);
}

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

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

/* Header Styles */
header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 2rem 0;
    margin-bottom: 2rem;
    border-radius: 0 0 20px 20px;
    box-shadow: var(--card-shadow);
}

header h1 {
    font-weight: 700;
    letter-spacing: -1px;
    margin: 0;
}

/* Navigation */
nav {
    background: white;
    padding: 1rem;
    border-radius: 10px;
    box-shadow: var(--card-shadow);
    margin-bottom: 2rem;
}

.nav-pills .nav-link {
    color: var(--dark-color);
    margin: 0 0.5rem;
    border-radius: 25px;
    transition: all 0.3s ease;
}

.nav-pills .nav-link:hover {
    background-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.nav-pills .nav-link.active {
    background-color: var(--primary-color);
}

/* Card Styles */
.card {
    border: none;
    border-radius: 15px;
    box-shadow: var(--card-shadow);
    transition: all 0.3s ease;
    margin-bottom: 1.5rem;
}

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

.card-header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    border-radius: 15px 15px 0 0 !important;
    font-weight: 600;
}

/* Form Styles */
.form-control, .form-select {
    border-radius: 10px;
    border: 2px solid #e0e0e0;
    padding: 12px 15px;
    transition: all 0.3s ease;
}

.form-control:focus, .form-select:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(74, 144, 226, 0.25);
}

.form-label {
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 0.5rem;
}

/* Button Styles */
.btn {
    border-radius: 25px;
    padding: 10px 30px;
    font-weight: 600;
    transition: all 0.3s ease;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    border: none;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(74, 144, 226, 0.4);
}

.btn-secondary {
    background-color: #6c757d;
    border: none;
}

/* Result Box */
.result-box {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    border-radius: 15px;
    padding: 2rem;
    margin-top: 1.5rem;
    box-shadow: var(--card-shadow);
}

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

.result-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: rgba(255, 255, 255, 0.8);
    border-radius: 10px;
    margin-bottom: 0.8rem;
}

.result-label {
    font-weight: 600;
    color: var(--dark-color);
}

.result-value {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary-color);
}

/* Footer */
footer {
    background-color: var(--dark-color);
    color: white;
    padding: 2rem 0;
    margin-top: 3rem;
    border-radius: 20px 20px 0 0;
}

/* Responsive */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }
    
    .nav-pills .nav-link {
        margin: 0.2rem;
        font-size: 0.9rem;
    }
    
    .card {
        margin-bottom: 1rem;
    }
}

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

.fade-in {
    animation: fadeIn 0.5s ease-out;
}

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.category-card {
    background: white;
    border-radius: 15px;
    padding: 1.5rem;
    box-shadow: var(--card-shadow);
    transition: all 0.3s ease;
}

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

.category-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.category-card ul {
    list-style: none;
    padding: 0;
}

.category-card ul li {
    padding: 0.5rem 0;
    border-bottom: 1px solid #eee;
}

.category-card ul li:last-child {
    border-bottom: none;
}

.category-card ul li a {
    color: var(--dark-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

.category-card ul li a:hover {
    color: var(--primary-color);
    padding-left: 10px;
}