:root {
    --primary-color: #4a6fa5;
    --secondary-color: #166088;
    --accent-color: #4cb5f5;
    --background-color: #f5f7fa;
    --card-background: #ffffff;
    --text-color: #333333;
    --border-color: #e1e5eb;
    --success-color: #28a745;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 30px;
    padding: 20px 0;
    border-bottom: 1px solid var(--border-color);
}

header h1 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.last-updated {
    color: #666;
    font-size: 0.9rem;
}

.dashboard {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.card {
    background-color: var(--card-background);
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    padding: 20px;
    text-align: center;
    transition: transform 0.3s ease;
}

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

.card h2 {
    font-size: 1.2rem;
    color: var(--secondary-color);
    margin-bottom: 15px;
}

.balance-value, .usage-value, .days-value {
    font-size: 2.5rem;
    font-weight: bold;
    margin: 10px 0;
}

.current-balance .balance-value {
    color: var(--primary-color);
}

.daily-usage .usage-value {
    color: var(--accent-color);
}

.avg-usage .usage-value {
    color: var(--secondary-color);
}

.estimated-days .days-value {
    color: var(--success-color);
}

.unit {
    font-size: 1rem;
    color: #666;
}

.chart-container {
    background-color: var(--card-background);
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    padding: 20px;
    margin-bottom: 30px;
}

.chart-container h2 {
    color: var(--secondary-color);
    margin-bottom: 20px;
    font-size: 1.3rem;
}

.data-table {
    background-color: var(--card-background);
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    padding: 20px;
    margin-bottom: 30px;
    overflow-x: auto;
}

.data-table h2 {
    color: var(--secondary-color);
    margin-bottom: 20px;
    font-size: 1.3rem;
}

table {
    width: 100%;
    border-collapse: collapse;
}

table th, table td {
    padding: 12px 15px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

table th {
    background-color: var(--primary-color);
    color: white;
}

table tr:nth-child(even) {
    background-color: rgba(0, 0, 0, 0.02);
}

table tr:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

footer {
    text-align: center;
    padding: 20px;
    margin-top: 30px;
    color: #666;
    font-size: 0.9rem;
    border-top: 1px solid var(--border-color);
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .dashboard {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .dashboard {
        grid-template-columns: 1fr;
    }
    
    .balance-value, .usage-value, .days-value {
        font-size: 2rem;
    }
    
    .card h2 {
        font-size: 1rem;
    }
}

/* Low balance warning */
.low-balance {
    color: var(--danger-color) !important;
}

.medium-balance {
    color: var(--warning-color) !important;
}