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

:root {
    --primary-color: #2563eb;
    --secondary-color: #3b82f6;
    --accent-color: #60a5fa;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: var(--text-primary);
}

header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    text-align: center;
    padding: 2rem 1rem;
    box-shadow: var(--shadow-lg);
    position: sticky;
    top: 0;
    z-index: 100;
}

header h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    font-weight: 700;
}

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

nav {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    padding: 1rem;
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 120px;
    z-index: 90;
}

.nav-btn {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem 1rem;
    margin: 0.25rem;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-primary);
}

.nav-btn:hover {
    background: var(--accent-color);
    color: white;
    border-color: var(--accent-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.nav-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

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

.chart-container {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 16px;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    margin-bottom: 2rem;
}

.chart-header {
    text-align: center;
    margin-bottom: 2rem;
}

.chart-header h2 {
    font-size: 1.8rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.chart-header p {
    color: var(--text-secondary);
    font-size: 1rem;
}

.chart-wrapper {
    position: relative;
    height: 400px;
    margin: 0 auto;
}

.controls {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    margin-bottom: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.control-group label {
    font-weight: 500;
    color: var(--text-primary);
}

.control-group select,
.control-group button {
    padding: 0.5rem 1rem;
    border-radius: 8px;
    border: 2px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.9rem;
}

.control-group button {
    background: var(--secondary-color);
    color: white;
    border-color: var(--secondary-color);
}

.control-group button:hover {
    background: var(--accent-color);
    border-color: var(--accent-color);
    transform: translateY(-1px);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 12px;
    padding: 1.5rem;
    text-align: center;
    box-shadow: var(--shadow-md);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

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

.stat-card h3 {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.stat-card p {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

footer {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    text-align: center;
    padding: 2rem 1rem;
    box-shadow: var(--shadow-lg);
    color: var(--text-secondary);
}

@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }
    
    .nav-btn {
        padding: 0.5rem 0.75rem;
        font-size: 0.8rem;
        margin: 0.125rem;
    }
    
    .chart-container {
        padding: 1rem;
    }
    
    .chart-wrapper {
        height: 300px;
    }
    
    .controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .control-group {
        justify-content: center;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .nav-btn {
        font-size: 0.7rem;
        padding: 0.4rem 0.6rem;
    }
}

.chart-loading {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 400px;
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.chart-loading::after {
    content: '';
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    margin-left: 10px;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}