:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --secondary: #64748b;
    --bg: #f8fafc;
    --text: #1e293b;
    --white: #ffffff;
    --accent: #10b981;
    --danger: #ef4444;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background-color: var(--bg);
}

header {
    background: var(--white);
    border-bottom: 1px solid #e2e8f0;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    text-decoration: none;
}

nav a {
    margin-left: 1.5rem;
    text-decoration: none;
    color: var(--secondary);
    font-weight: 500;
    transition: color 0.2s;
}

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

.container {
    max-width: 1000px;
    margin: 3rem auto;
    padding: 0 1.5rem;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    text-align: center;
}

.subtitle {
    text-align: center;
    color: var(--secondary);
    margin-bottom: 3rem;
    font-size: 1.1rem;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.card {
    background: var(--white);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid #e2e8f0;
    transition: transform 0.2s, box-shadow 0.2s;
    text-decoration: none;
    color: inherit;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

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

.btn {
    display: inline-block;
    background: var(--primary);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 600;
    margin-top: 1rem;
    border: none;
    cursor: pointer;
    text-align: center;
}

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

.calculator-box {
    background: white;
    padding: 2rem;
    border-radius: 16px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    max-width: 600px;
    margin: 0 auto;
}

.input-group {
    margin-bottom: 1.5rem;
}

.input-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
}

.input-group input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font-size: 1rem;
}

.results {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 2px dashed #e2e8f0;
}

.result-item {
    display: flex;
    justify-content: space-between;
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

.result-highlight {
    color: var(--accent);
    font-weight: 700;
}

.affiliate-box {
    background: #eff6ff;
    border: 1px solid #bfdbfe;
    padding: 1.5rem;
    border-radius: 12px;
    margin-top: 2rem;
}

footer {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--secondary);
    font-size: 0.9rem;
}

@media (max-width: 600px) {
    .card-grid { grid-template-columns: 1fr; }
}