:root {
    /* Color Palette - Premium Modern */
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --background-color: #f8fafc;
    --surface-color: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --danger-color: #ef4444;
    --success-color: #10b981;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    --sidebar-width: 260px;
    --header-height: 70px;
}

[data-theme="dark"] {
    --primary-color: #3b82f6;
    --primary-hover: #60a5fa;
    --background-color: #0f172a;
    --surface-color: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --border-color: #334155;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Inter', sans-serif;
}

body {
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background-color 0.3s ease;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    color: var(--text-primary);
}

a {
    color: var(--primary-color);
    text-decoration: none;
}

/* Layout */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--surface-color);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    transition: all 0.3s ease;
    z-index: 50;
}

.sidebar-header {
    height: var(--header-height);
    display: flex;
    align-items: center;
    padding: 0 1.5rem;
    border-bottom: 1px solid var(--border-color);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--primary-color);
}

.sidebar-nav {
    flex: 1;
    padding: 1rem 0.5rem;
    overflow-y: auto;
}

.nav-item {
    display: flex;
    align-items: center;
    padding: 0.75rem 1rem;
    margin-bottom: 0.25rem;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.nav-item i {
    margin-right: 0.75rem;
    width: 20px;
    height: 20px;
}

.nav-item:hover {
    background-color: rgba(37, 99, 235, 0.05);
    color: var(--primary-color);
}

.nav-item.active {
    background-color: rgba(37, 99, 235, 0.1);
    color: var(--primary-color);
    font-weight: 600;
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 0;
}

/* Header */
.top-header {
    height: var(--header-height);
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 2rem;
    box-shadow: var(--shadow-sm);
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
}

.user-info {
    display: flex;
    flex-direction: column;
}

.user-name {
    font-weight: 600;
    font-size: 0.9rem;
}

.user-role {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* Page Level Content */
.page-container {
    padding: 2rem;
    flex: 1;
    overflow-y: auto;
}

.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    gap: 0.5rem;
}

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

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

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

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

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

/* Cards & Forms */
.card {
    background-color: var(--surface-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.form-group {
    margin-bottom: 1.25rem;
}

.form-label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    font-size: 0.875rem;
}

.form-control {
    width: 100%;
    padding: 0.625rem 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background-color: var(--background-color);
    color: var(--text-primary);
    font-size: 0.875rem;
    transition: border-color 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Tables */
.table-responsive {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
}

th {
    background-color: rgba(0,0,0,0.02);
    padding: 0.75rem 1rem;
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-color);
}

td {
    padding: 1rem;
    font-size: 0.875rem;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-primary);
}

tr:hover td {
    background-color: rgba(0,0,0,0.01);
}

/* Login Page specifically */
.login-container {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
}

.login-card {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    padding: 3rem;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 400px;
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.login-card h1 {
    margin-bottom: 0.5rem;
    color: var(--primary-color);
}

.login-card p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

/* Modals */
.modal-overlay {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: rgba(0,0,0,0.5);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 100;
    backdrop-filter: blur(4px);
    opacity: 0;
    transition: opacity 0.3s;
}

.modal-overlay.active {
    display: flex;
    opacity: 1;
}

.modal-content {
    background-color: var(--surface-color);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    transform: scale(0.95);
    transition: transform 0.3s;
}

.modal-overlay.active .modal-content {
    transform: scale(1);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.close-modal {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-secondary);
}

/* Utility */
.d-none { display: none !important; }
.text-center { text-align: center; }
.mb-3 { margin-bottom: 1rem; }
.mb-4 { margin-bottom: 1.5rem; }
.gap-2 { gap: 0.5rem; display: flex; }
.gap-3 { gap: 1rem; display: flex; }
.flex-wrap { flex-wrap: wrap; }

/* Mobile Responsive */
.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    align-items: center;
    justify-content: center;
}

.mobile-menu-btn i {
    width: 24px;
    height: 24px;
}

@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        left: -100%;
        top: 0;
        bottom: 0;
        box-shadow: var(--shadow-lg);
        background-color: var(--surface-color);
        width: 280px;
        max-width: 80vw;
    }
    
    .sidebar.active {
        left: 0;
    }

    .mobile-menu-btn {
        display: flex;
    }
    
    .top-header {
        padding: 0 1rem;
        justify-content: space-between;
    }
    
    .d-none-mobile {
        display: none !important;
    }
}