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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
}

header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem 2rem;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    margin-bottom: 1rem;
    color: #2c3e50;
    font-size: 2.2rem;
}

nav {
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.nav-btn {
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 25px;
    background: #ecf0f1;
    color: #34495e;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 1rem;
    font-weight: 500;
}

.nav-btn:hover {
    background: #3498db;
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
}

.nav-btn.active {
    background: #e74c3c;
    color: white;
    box-shadow: 0 4px 15px rgba(231, 76, 60, 0.3);
}

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

.chart-container {
    background: white;
    border-radius: 15px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    height: 500px;
}

.data-controls {
    background: white;
    border-radius: 15px;
    padding: 1.5rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 1rem;
}

label {
    font-weight: 600;
    color: #2c3e50;
}

select, button {
    padding: 0.7rem 1.2rem;
    border: 2px solid #ecf0f1;
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

select {
    background: white;
    color: #2c3e50;
    min-width: 150px;
}

select:focus {
    outline: none;
    border-color: #3498db;
}

button {
    background: #3498db;
    color: white;
    border: none;
    cursor: pointer;
    font-weight: 500;
}

button:hover {
    background: #2980b9;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
}

#resetDataBtn {
    background: #e74c3c;
}

#resetDataBtn:hover {
    background: #c0392b;
    box-shadow: 0 4px 15px rgba(231, 76, 60, 0.3);
}

@media (max-width: 768px) {
    .data-controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .control-group {
        justify-content: center;
    }
    
    .chart-container {
        height: 400px;
        padding: 1rem;
    }
    
    h1 {
        font-size: 1.8rem;
    }
    
    nav {
        gap: 0.5rem;
    }
    
    .nav-btn {
        padding: 0.6rem 1rem;
        font-size: 0.9rem;
    }
}