:root {
    --primary-color: #2563eb;
    --secondary-color: #64748b;
    --success-color: #059669;
    --warning-color: #d97706;
    --danger-color: #dc2626;
    --light-bg: #f8fafc;
    --dark-text: #1e293b;
}

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

.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

.login-card {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.1);
    overflow: hidden;
    max-width: 400px;
    width: 100%;
}

.login-header {
    background: linear-gradient(135deg, var(--primary-color), #3b82f6);
    color: white;
    padding: 2rem;
    text-align: center;
}

.dashboard-container {
    background: var(--light-bg);
    min-height: 100vh;
}

.sidebar {
    background: white;
    box-shadow: 2px 0 10px rgba(0,0,0,0.1);
    min-height: 100vh;
    position: fixed;
    width: 250px;
    z-index: 1000;
}

.main-content {
    margin-left: 250px;
    padding: 2rem;
}

.navbar-custom {
    background: white;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-left: 250px;
}

.card-custom {
    border: none;
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.08);
    transition: transform 0.3s ease;
}

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

.stat-card {
    background: linear-gradient(135deg, var(--primary-color), #3b82f6);
    color: white;
    border-radius: 15px;
    padding: 1.5rem;
}

.btn-custom {
    border-radius: 10px;
    padding: 0.5rem 1.5rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.table-custom {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0,0,0,0.08);
}

.nav-link-custom {
    color: var(--dark-text);
    padding: 0.75rem 1.5rem;
    border-radius: 10px;
    margin: 0.25rem;
    transition: all 0.3s ease;
}

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

.form-control-custom {
    border-radius: 10px;
    border: 2px solid #e2e8f0;
    padding: 0.75rem;
}

.form-control-custom:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(37, 99, 235, 0.25);
}

.modal-custom .modal-content {
    border-radius: 15px;
    border: none;
}

.badge-custom {
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-weight: 500;
}

.hidden {
    display: none !important;
}

.grade-input {
    width: 80px;
    text-align: center;
}

.report-card {
    background: white;
    border-radius: 15px;
    padding: 2rem;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
        transition: transform 0.3s ease;
    }
    
    .sidebar.show {
        transform: translateX(0);
    }
    
    .main-content, .navbar-custom {
        margin-left: 0;
    }
}