:root {
    --primary-color: #667eea;
    --primary-dark: #5568d3;
    --secondary-color: #764ba2;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    
    --bg-color: #f8f9fa;
    --surface-color: #ffffff;
    --text-color: #1f2937;
    --text-muted: #6b7280;
    --border-color: #e5e7eb;
    
    --header-height: 70px;
    --sidebar-width: 250px;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
}

/* Header Styles */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    height: var(--header-height);
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.header-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 30px;
}

.site-title {
    font-size: 1.5rem;
    font-weight: 700;
    text-decoration: none;
    color: white;
    display: flex;
    align-items: center;
    gap: 10px;
}

.main-nav {
    display: flex;
    gap: 5px;
    list-style: none;
}

.main-nav a {
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
    padding: 10px 20px;
    border-radius: var(--radius-md);
    transition: all 0.2s;
    font-weight: 500;
}

.main-nav a:hover {
    background: rgba(255, 255, 255, 0.15);
    color: white;
}

.main-nav a.active {
    background: rgba(255, 255, 255, 0.2);
    color: white;
}

.header-right {
    display: flex;
    align-items: center;
    gap: 20px;
}

.user-info {
    display: flex;
    align-items: center;
    gap: 10px;
    color: rgba(255, 255, 255, 0.9);
}

.user-avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.2);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
}

.btn-logout {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s;
    text-decoration: none;
    display: inline-block;
}

.btn-logout:hover {
    background: rgba(255, 255, 255, 0.3);
}

/* Main Content */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 30px 20px;
}

/* Page Header */
.page-header {
    margin-bottom: 30px;
}

.page-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-color);
    margin-bottom: 10px;
}

.page-subtitle {
    color: var(--text-muted);
    font-size: 1rem;
}

/* Tabs */
.tabs {
    border-bottom: 2px solid var(--border-color);
    margin-bottom: 30px;
}

.tabs-nav {
    display: flex;
    gap: 10px;
    list-style: none;
}

.tabs-nav a {
    color: var(--text-muted);
    text-decoration: none;
    padding: 12px 24px;
    border-bottom: 3px solid transparent;
    transition: all 0.2s;
    font-weight: 500;
    display: block;
    margin-bottom: -2px;
}

.tabs-nav a:hover {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.tabs-nav a.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

/* Cards */
.card {
    background: var(--surface-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    padding: 24px;
    margin-bottom: 20px;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-color);
}

/* Buttons */
.btn {
    padding: 10px 20px;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.2s;
    text-decoration: none;
    display: inline-block;
    text-align: center;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--text-muted);
    color: white;
}

.btn-secondary:hover {
    background: var(--text-color);
}

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

.btn-danger {
    background: var(--danger-color);
    color: white;
}

.btn-danger:hover {
    background: #dc2626;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.875rem;
}

/* Forms */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-color);
}

.form-control {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    transition: all 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.form-select {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    background: white;
    cursor: pointer;
}

.form-checkbox {
    display: flex;
    align-items: center;
    gap: 8px;
}

.form-checkbox input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
}

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

.table thead {
    background: var(--bg-color);
}

.table th {
    padding: 12px;
    text-align: left;
    font-weight: 600;
    color: var(--text-color);
    border-bottom: 2px solid var(--border-color);
}

.table td {
    padding: 12px;
    border-bottom: 1px solid var(--border-color);
}

.table tbody tr:hover {
    background: var(--bg-color);
}

/* Badges */
.badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 0.85rem;
    font-weight: 500;
}

.badge-success {
    background: #d1fae5;
    color: #065f46;
}

.badge-danger {
    background: #fee2e2;
    color: #991b1b;
}

.badge-primary {
    background: #dbeafe;
    color: #1e40af;
}

.badge-warning {
    background: #fef3c7;
    color: #92400e;
}

/* Alerts */
.alert {
    padding: 14px 18px;
    border-radius: var(--radius-md);
    margin-bottom: 20px;
}

.alert-success {
    background: #d1fae5;
    color: #065f46;
    border-left: 4px solid var(--success-color);
}

.alert-error {
    background: #fee2e2;
    color: #991b1b;
    border-left: 4px solid var(--danger-color);
}

.alert-info {
    background: #dbeafe;
    color: #1e40af;
    border-left: 4px solid var(--info-color);
}

/* Login Page Specific */
.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    padding: 20px;
}

.login-card {
    background: white;
    border-radius: var(--radius-xl);
    padding: 40px;
    max-width: 420px;
    width: 100%;
    box-shadow: var(--shadow-xl);
}

.login-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-color);
    margin-bottom: 10px;
    text-align: center;
}

.login-subtitle {
    color: var(--text-muted);
    text-align: center;
    margin-bottom: 30px;
}

/* Utilities */
.text-center {
    text-align: center;
}

.mt-20 {
    margin-top: 20px;
}

.mb-20 {
    margin-bottom: 20px;
}

.flex {
    display: flex;
}

.justify-between {
    justify-content: space-between;
}

.items-center {
    align-items: center;
}

.gap-10 {
    gap: 10px;
}