:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --light-color: #ecf0f1;
    --dark-color: #2c3e50;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    margin: 0;
    padding: 0;
    background-color: #f5f5f5;
}

header {
    background: var(--primary-color);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

nav {
    background: var(--secondary-color);
    padding: 1rem;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    padding: 0;
    margin: 0;
}

nav li {
    margin: 0 1rem;
}

nav a {
    color: white;
    text-decoration: none;
    font-weight: bold;
}

nav a:hover {
    text-decoration: underline;
}

main {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
}

section {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    padding: 2rem;
    margin-bottom: 2rem;
}

h1, h2, h3 {
    color: var(--primary-color);
}

.controls {
    background: var(--light-color);
    padding: 1rem;
    border-radius: 5px;
    margin-bottom: 1rem;
}

.controls label {
    margin-right: 1rem;
}

.chart-container {
    display: flex;
    flex-wrap: wrap;
    gap: 2rem;
}

.chart-container > div {
    flex: 1;
    min-width: 300px;
}

canvas {
    width: 100%;
    height: 300px;
    background: white;
    border: 1px solid #ddd;
}

footer {
    text-align: center;
    padding: 1rem;
    background: var(--dark-color);
    color: white;
}

@media (max-width: 768px) {
    nav ul {
        flex-direction: column;
        align-items: center;
    }
    
    nav li {
        margin: 0.5rem 0;
    }
    
    .chart-container {
        flex-direction: column;
    }
}