:root {
    --primary: #1e3a5f;
    --primary-light: #2c5282;
    --primary-dark: #0f2640;
    --accent: #38a169;
    --bg: #f7fafc;
    --card-bg: #ffffff;
    --text: #2d3748;
    --text-muted: #718096;
    --border: #e2e8f0;
}

body {
    background-color: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft JhengHei", sans-serif;
}

.bg-primary-custom {
    background: linear-gradient(135deg, var(--primary), var(--primary-light)) !important;
}

.navbar-brand {
    font-size: 1.3rem;
    letter-spacing: 1px;
}

.card {
    border: none;
    border-radius: 12px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    transition: box-shadow 0.2s;
}

.card:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
}

.card-header {
    background-color: var(--primary);
    color: white;
    border-radius: 12px 12px 0 0 !important;
    font-weight: 600;
}

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

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

.btn-success {
    background-color: var(--accent);
    border-color: var(--accent);
}

.stat-card {
    border-left: 4px solid var(--primary);
    padding: 1rem 1.5rem;
}

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

.stat-card .stat-label {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.table th {
    background-color: var(--primary);
    color: white;
    font-weight: 500;
    border: none;
}

.table td {
    vertical-align: middle;
}

.badge-grade-a {
    background-color: #38a169;
    color: white;
}

.badge-grade-b {
    background-color: #3182ce;
    color: white;
}

.badge-grade-c {
    background-color: #e53e3e;
    color: white;
}

.badge-grade-retrain {
    background-color: #d69e2e;
    color: white;
}

.sidebar-link {
    display: block;
    padding: 0.6rem 1rem;
    color: var(--text);
    text-decoration: none;
    border-radius: 8px;
    transition: background 0.15s;
}

.sidebar-link:hover, .sidebar-link.active {
    background-color: var(--primary);
    color: white;
}

.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
}

.login-card {
    width: 100%;
    max-width: 420px;
    border-radius: 16px;
    padding: 2.5rem;
    background: white;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.login-card h2 {
    color: var(--primary);
    font-weight: 700;
}

@media (max-width: 768px) {
    .container-fluid {
        padding-left: 0.5rem;
        padding-right: 0.5rem;
    }
    .stat-card .stat-value {
        font-size: 1.5rem;
    }
}

.dropdown-menu {
    border: none;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
    border-radius: 10px;
}

.dropdown-item:hover {
    background-color: var(--primary);
    color: white;
}