:root {
    --primary-color: #2c5aa0;
    --secondary-color: #f8f9fc;
    --accent-color: #36b9cc;
    --text-primary: #2e3440;
    --text-secondary: #6c757d;
    --sidebar-width: 280px;
    --header-height: 70px;
    --shadow-light: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-medium: 0 4px 6px rgba(0,0,0,0.1);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--secondary-color);
    color: var(--text-primary);
    overflow-x: hidden;
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: linear-gradient(135deg, var(--primary-color) 0%, #1e3a8a 100%);
    color: white;
    z-index: 1050;
    box-shadow: var(--shadow-medium);
    display: flex;
    align-items: center;
    padding: 0 1.5rem;
}

.sidebar-toggle {
    background: none;
    border: none;
    color: white;
    font-size: 1.2rem;
    margin-right: 1rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 8px;
    transition: var(--transition);
}

    .sidebar-toggle:hover {
        background-color: rgba(255, 255, 255, 0.1);
    }

.header-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0;
    background: linear-gradient(45deg, #ffffff, #e0e7ff);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-actions {
    margin-left: auto;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: rgba(255, 255, 255, 0.9);
}

/* Sidebar */
.sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: var(--sidebar-width);
    height: calc(100vh - var(--header-height));
    background: white;
    box-shadow: var(--shadow-medium);
    transform: translateX(0);
    transition: var(--transition);
    z-index: 1040;
    overflow-y: auto;
}

    .sidebar.collapsed {
        transform: translateX(-100%);
    }

.sidebar-nav {
    padding: 1.5rem 0;
}

.nav-section {
    margin-bottom: 2rem;
}

.nav-section-title {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 1px;
    padding: 0 1.5rem;
    margin-bottom: 0.75rem;
}

.nav-item {
    margin: 0.25rem 1rem;
}

.nav-link {
    display: flex;
    align-items: center;
    padding: 0.875rem 1rem;
    color: var(--text-primary);
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: var(--transition);
    font-weight: 500;
    position: relative;
    overflow: hidden;
}

    .nav-link:hover {
        background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
        color: white;
        transform: translateX(4px);
        box-shadow: var(--shadow-light);
    }

    .nav-link.active {
        background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
        color: white;
        box-shadow: var(--shadow-light);
    }

    .nav-link i {
        width: 20px;
        text-align: center;
        margin-right: 0.75rem;
        font-size: 1rem;
    }

/* Main Content */
.main-content {
    margin-left: var(--sidebar-width);
    margin-top: var(--header-height);
    padding: 2rem;
    min-height: calc(100vh - var(--header-height));
    transition: var(--transition);
}

    .main-content.expanded {
        margin-left: 0;
    }

/* Content Container */
.content-container {
    background: white;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-light);
    padding: 2rem;
    min-height: 500px;
}

/* Overlay for mobile */
.sidebar-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1030;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
}

    .sidebar-overlay.show {
        opacity: 1;
        visibility: visible;
    }

/* Responsive Design */
@media (max-width: 768px) {
    : root {
        --sidebar-width: 280px;
    }

    .sidebar {
        transform: translateX(-100%);
        box-shadow: var(--shadow-medium);
    }

        .sidebar.show {
            transform: translateX(0);
        }

    .main-content {
        margin-left: 0;
        padding: 1rem;
    }

    .content-container {
        padding: 1.5rem;
    }

    .header {
        padding: 0 1rem;
    }

    .header-title {
        font-size: 1.25rem;
    }

    .user-info {
        display: none;
    }
}

@media (max-width: 576px) {
    .main-content {
        padding: 0.75rem;
    }

    .content-container {
        padding: 1rem;
        border-radius: 8px;
    }

    .sidebar-nav {
        padding: 1rem 0;
    }

    .nav-link {
        padding: 0.75rem;
        margin: 0.125rem 0.75rem;
    }
}

/* Loading Animation */
.loading-spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* Custom Scrollbar */
.sidebar::-webkit-scrollbar {
    width: 6px;
}

.sidebar::-webkit-scrollbar-track {
    background: transparent;
}

.sidebar::-webkit-scrollbar-thumb {
    background: rgba(0, 0, 0, 0.1);
    border-radius: 3px;
}

    .sidebar::-webkit-scrollbar-thumb:hover {
        background: rgba(0, 0, 0, 0.2);
    }