:root {
    --primary: #3498db;
    --primary-dark: #2980b9;
    --light: #f8f9fa;
    --dark: #343a40;
    --danger: #dc3545;
    --success: #28a745;
    --border: #dee2e6;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark);
    background-color: #f5f7fa;
    margin: 0;
    padding: 0;
}

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

/* Header */
header {
    background-color: white;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    padding: 15px 0;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.nav-links {
    display: flex;
    gap: 20px;
}

.nav-links a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
}

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

/* Cards */
.card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    padding: 20px;
    margin-bottom: 20px;
}

/* Forms */
.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
}

.form-control {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 16px;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 10px 20px;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    text-decoration: none;
    font-size: 16px;
}

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

.btn.sm {
    padding: 5px 10px;
    font-size: 14px;
}

/* Tables */
.table {
    width: 100%;
    border-collapse: collapse;
}

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

.table th {
    background-color: var(--light);
    font-weight: 600;
}

/* Alerts */
.alert {
    padding: 15px;
    border-radius: 4px;
    margin-bottom: 20px;
}

.alert.success {
    background-color: #d4edda;
    color: #155724;
}

.alert.error {
    background-color: #f8d7da;
    color: #721c24;
}

/* Dashboard */
.dashboard {
    padding: 20px;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    text-align: center;
}

.stat-card h3 {
    font-size: 1rem;
    color: #6c757d;
    margin-bottom: 10px;
}

.stat-card p {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--dark);
    margin: 0;
}

.chart-container {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}

.recent-payments {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

/* Login */
.login-container {
    max-width: 400px;
    margin: 50px auto;
    padding: 30px;
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.login-container h1 {
    text-align: center;
    margin-bottom: 30px;
    color: var(--primary);
}