:root {
    --primary-color: #2c3e50;
    --secondary-color: #34495e;
    --accent-color: #3498db;
    --success-color: #27ae60;
    --warning-color: #f39c12;
    --danger-color: #c0392b;
    --light-bg: #f8f9fa;
    --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --hover-shadow: 0 8px 15px rgba(0, 0, 0, 0.1);
}

body {
    background-color: #f4f6f9;
    font-family: 'Segoe UI', 'Microsoft YaHei', sans-serif;
    color: #333;
}

/* Navbar */
.navbar {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color)) !important;
    box-shadow: 0 2px 10px rgba(0,0,0,0.2);
    padding: 1rem 0;
}

.navbar-brand {
    font-weight: 700;
    letter-spacing: 1px;
    font-size: 1.5rem;
}

.nav-link {
    font-weight: 500;
    transition: color 0.3s;
}

.nav-link:hover {
    color: var(--accent-color) !important;
}

/* Cards */
.card {
    border: none;
    border-radius: 12px;
    box-shadow: var(--card-shadow);
    transition: transform 0.3s, box-shadow 0.3s;
    background: white;
    overflow: hidden;
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: var(--hover-shadow);
}

.card-header {
    background-color: white;
    border-bottom: 1px solid rgba(0,0,0,0.05);
    font-weight: 700;
    padding: 1.2rem;
    font-size: 1.1rem;
}

.card-header.bg-primary {
    background: linear-gradient(135deg, var(--accent-color), #2980b9) !important;
    color: white;
    border: none;
}

/* Buttons */
.btn {
    border-radius: 8px;
    padding: 0.5rem 1.2rem;
    font-weight: 600;
    transition: all 0.3s;
}

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

.btn-primary:hover {
    background-color: #2980b9;
    border-color: #2980b9;
    transform: translateY(-1px);
}

/* Tables */
.table {
    margin-bottom: 0;
}

.table thead th {
    background-color: #f8f9fa;
    border-bottom: 2px solid #e9ecef;
    color: #6c757d;
    font-weight: 600;
    text-transform: uppercase;
    font-size: 0.85rem;
    letter-spacing: 0.5px;
}

.table-hover tbody tr:hover {
    background-color: rgba(52, 152, 219, 0.05);
}

/* Forms */
.form-control {
    border-radius: 8px;
    padding: 0.75rem;
    border: 1px solid #dee2e6;
}

.form-control:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 0.2rem rgba(52, 152, 219, 0.25);
}

.form-label, .control-label {
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: #555;
}

/* Utilities */
.text-primary {
    color: var(--accent-color) !important;
}

.page-header {
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid #e9ecef;
}