:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --sidebar-bg: #2d3748;
    --sidebar-hover: #4a5568;
}
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: #f4f6f9;
}
.sidebar {
    height: 100vh;
    width: 250px;
    position: fixed;
    top: 0;
    left: 0;
    background: var(--sidebar-bg);
    color: #fff;
    transition: all 0.3s;
    overflow-y: auto;
    z-index: 1000;
}
.sidebar-brand {
    padding: 20px 15px;
    font-size: 1.5rem;
    font-weight: bold;
    background: var(--primary-gradient);
    text-align: center;
}
.sidebar-menu {
    list-style: none;
    padding: 0;
    margin: 0;
}
.sidebar-menu li a {
    display: block;
    padding: 12px 20px;
    color: #cbd5e0;
    text-decoration: none;
    transition: 0.3s;
}
.sidebar-menu li a:hover {
    background: var(--sidebar-hover);
    color: #fff;
}
.sidebar-menu li a i {
    margin-right: 10px;
    width: 20px;
    text-align: center;
}
.main-content {
    margin-left: 250px;
    transition: all 0.3s;
}
@media (max-width: 768px) {
    .sidebar {
        left: -250px;
    }
    .sidebar.active {
        left: 0;
    }
    .main-content {
        margin-left: 0;
    }
}
.card {
    border-radius: 12px;
    box-shadow: 0 0 20px rgba(0,0,0,0.05);
    transition: transform 0.2s;
}
.card:hover {
    transform: translateY(-5px);
}
.card .card-header {
    background: var(--primary-gradient);
    color: #fff;
    border-radius: 12px 12px 0 0;
}