:root {
    --bg-color: #f4f6f9;
    --sidebar-bg: #ffffff;
    --header-bg: #ffffff;
    --card-bg: #ffffff;
    --text-color: #212529;
    --text-muted: #6c757d;
    --accent-color: #6f42c1;
    --accent-hover: #5a32a3;
    --border-color: #e9ecef;
    --input-bg: #ffffff;
    --shadow: 0 0.125rem 0.25rem rgba(0, 0, 0, 0.075);
    --sidebar-width: 250px;
    --header-height: 60px;
}

[data-theme="dark"] {
    --bg-color: #121212;
    --sidebar-bg: #1e1e1e;
    --header-bg: #1e1e1e;
    --card-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --text-muted: #a0a0a0;
    --accent-color: #a862cc;
    --accent-hover: #be7fe0;
    --border-color: #333333;
    --input-bg: #2d2d2d;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
}

* {
    box-sizing: border-box;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    margin: 0;
    padding: 0;
    overflow-x: hidden;
}

/* App Wrapper */
.app-wrapper {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    position: fixed;
    height: 100vh;
    transition: transform 0.3s ease-in-out;
    z-index: 1000;
}

.sidebar-header {
    height: var(--header-height);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 20px;
    border-bottom: 1px solid var(--border-color);
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--accent-color);
}

.sidebar-nav {
    flex: 1;
    padding: 20px 0;
    overflow-y: auto;
}

.nav-link {
    display: flex;
    align-items: center;
    padding: 12px 20px;
    color: var(--text-color);
    text-decoration: none;
    transition: background-color 0.2s, color 0.2s;
    font-weight: 500;
}

.nav-link .icon {
    margin-right: 12px;
    font-size: 1.1rem;
    width: 24px;
    text-align: center;
}

.nav-link:hover, .nav-link.active {
    background-color: rgba(111, 66, 193, 0.1); /* Light purple tint */
    color: var(--accent-color);
    border-right: 3px solid var(--accent-color);
}

[data-theme="dark"] .nav-link:hover, 
[data-theme="dark"] .nav-link.active {
    background-color: rgba(168, 98, 204, 0.15);
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border-color);
}

.nav-link.logout {
    color: #dc3545;
}
.nav-link.logout:hover {
    background-color: rgba(220, 53, 69, 0.1);
    border-right-color: #dc3545;
    color: #dc3545;
}

/* Main Content Area */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width); /* Offset for fixed sidebar */
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    transition: margin-left 0.3s ease-in-out;
}

/* Top Header */
.top-header {
    height: var(--header-height);
    background-color: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 20px;
    position: sticky;
    top: 0;
    z-index: 900;
}

.header-title {
    font-size: 1.1rem;
    font-weight: 600;
}

.user-info {
    display: flex;
    align-items: center;
}

.user-chip {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--text-color);
    padding: 5px 10px;
    border-radius: 20px;
    transition: background-color 0.2s;
}

.user-chip:hover {
    background-color: rgba(0,0,0,0.05);
}

[data-theme="dark"] .user-chip:hover {
    background-color: rgba(255,255,255,0.1);
}

.header-avatar, .header-avatar-placeholder {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    margin-right: 10px;
    object-fit: cover;
}

.header-avatar-placeholder {
    background-color: var(--accent-color);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
}

/* Content Wrapper */
.content-wrapper {
    padding: 30px;
    flex: 1;
}

/* Tiles (Cards) */
.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 24px;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

/* Dashboard Specific Tile Grid */
.dashboard-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 24px;
}

.stat-tile {
    text-align: center;
    cursor: pointer;
    text-decoration: none;
    display: block;
    color: var(--text-color);
}

.stat-tile:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 15px rgba(0,0,0,0.1);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent-color);
    margin: 10px 0;
}

.stat-label {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-muted);
}

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

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

input[type="text"],
input[type="password"],
input[type="email"],
input[type="file"],
select,
textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background-color: var(--input-bg);
    color: var(--text-color);
    font-size: 1rem;
    transition: border-color 0.2s;
}

input:focus, select:focus, textarea:focus {
    outline: none;
    border-color: var(--accent-color);
}

button {
    padding: 12px 24px;
    border-radius: 6px;
    border: none;
    cursor: pointer;
    font-weight: 600;
    transition: opacity 0.2s;
}

button[type="submit"], .btn-primary {
    background-color: var(--accent-color);
    color: white;
}

button:hover {
    opacity: 0.9;
}

.btn-danger {
    background-color: #dc3545;
    color: white;
    text-decoration: none;
    padding: 6px 12px;
    border-radius: 4px;
    font-size: 0.9rem;
}

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

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 16px;
    border-bottom: 1px solid var(--border-color);
    text-align: left;
}

th {
    color: var(--text-muted);
    font-weight: 600;
    text-transform: uppercase;
    font-size: 0.85rem;
}

/* Utilities */
.theme-toggle {
    width: 100%;
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    margin-bottom: 10px;
}

.icon-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-color);
    padding: 5px;
    cursor: pointer;
}

.alert-container {
    margin-bottom: 20px;
}
.alert {
    padding: 15px;
    background-color: rgba(111, 66, 193, 0.1);
    color: var(--accent-color);
    border: 1px solid var(--accent-color);
    border-radius: 6px;
}

/* Mobile / Responsive */
.mobile-only {
    display: none;
}

.sidebar-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 950;
    opacity: 0;
    transition: opacity 0.3s;
}

@media (max-width: 768px) {
    .mobile-only {
        display: block;
    }
    .desktop-only {
        display: none;
    }

    /* Sidebar is hidden by default on mobile */
    .sidebar {
        transform: translateX(-100%);
    }

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

    /* Open state */
    body.sidebar-open .sidebar {
        transform: translateX(0);
    }
    
    body.sidebar-open .sidebar-overlay {
        display: block;
        opacity: 1;
    }
    
    .content-wrapper {
        padding: 15px;
    }
    
    .dashboard-grid {
        grid-template-columns: 1fr;
    }
}