:root {
            --sidebar-width-expanded: 250px;
            --sidebar-width-collapsed: 70px;
            --bg-dark-main: #1d2127;
            --bg-dark-header: #171b1e;
            --bg-dark-hover: #242830;
            --accent-blue: #0088cc;
            --transition-speed: 0.25s;
        }

        body {
            background-color: #f4f7f6;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            margin: 0;
            padding: 0;
            overflow-x: hidden;
        }

        /* ================= SIDEBAR BASE STYLES ================= */
        .sidebar {
            width: var(--sidebar-width-expanded);
            background-color: var(--bg-dark-main);
            min-height: 100vh;
            color: #abb4be;
            position: fixed;
            top: 0;
            left: 0;
            z-index: 1050;
            transition: all var(--transition-speed) ease-in-out;
            white-space: nowrap;
            overflow-x: hidden;
            box-sizing: border-box;
        }

        .sidebar .brand {
            padding: 16px 20px;
            font-size: 18px;
            font-weight: bold;
            color: #fff;
            background-color: var(--bg-dark-header);
            display: flex;
            align-items: center;
            justify-content: space-between;
            height: 60px;
            box-sizing: border-box;
        }

        .sidebar .nav-item {
            position: relative;
            width: 100%;
            box-sizing: border-box;
        }

        .sidebar .nav-link {
            color: #abb4be;
            padding: 14px 20px;
            display: flex;
            align-items: center;
            border-bottom: 1px solid rgba(255, 255, 255, 0.05);
            transition: background var(--transition-speed) ease, color var(--transition-speed) ease;
            text-decoration: none;
            width: 100%;
            box-sizing: border-box;
        }

        .sidebar .nav-link:hover, .sidebar .nav-link.active {
            color: #fff;
            background-color: var(--bg-dark-hover);
            border-left: 4px solid var(--accent-blue);
            padding-left: 16px;
        }

        .sidebar .nav-icon {
            font-size: 18px;
            width: 24px;
            text-align: center;
            flex-shrink: 0;
        }

        .sidebar .nav-text {
            margin-left: 12px;
            transition: opacity var(--transition-speed) ease;
            overflow: hidden;
            text-overflow: ellipsis;
        }

        .sidebar-tooltip {
            display: none;
            position: absolute;
            left: 100%;
            top: 50%;
            transform: translateY(-50%);
            background-color: #000;
            color: #fff;
            padding: 6px 12px;
            border-radius: 4px;
            font-size: 13px;
            white-space: nowrap;
            z-index: 1060;
            pointer-events: none;
            box-shadow: 0 2px 6px rgba(0,0,0,0.3);
        }

        /* ================= SIDEBAR COLLAPSED STATE (DESKTOP) ================= */
        body.sidebar-collapsed .sidebar {
            width: var(--sidebar-width-collapsed);
        }

        body.sidebar-collapsed .sidebar .brand-text,
        body.sidebar-collapsed .sidebar .nav-text,
        body.sidebar-collapsed .sidebar .badge-count {
            display: none !important;
        }

        body.sidebar-collapsed .sidebar .brand {
            justify-content: center;
            padding: 16px 0;
        }

        body.sidebar-collapsed .sidebar .nav-link {
            justify-content: center;
            padding: 16px 0;
        }

        body.sidebar-collapsed .sidebar .nav-link:hover, 
        body.sidebar-collapsed .sidebar .nav-link.active {
            padding-left: 0;
        }

        body.sidebar-collapsed .sidebar .nav-icon {
            margin: 0;
        }

        body.sidebar-collapsed .sidebar .nav-item:hover .sidebar-tooltip {
            display: block;
        }

        /* ================= MAIN CONTENT STYLES ================= */
        .main-content {
            margin-left: var(--sidebar-width-expanded);
            transition: margin-left var(--transition-speed) ease-in-out;
            padding: 20px;
            min-height: 100vh;
        }

        body.sidebar-collapsed .main-content {
            margin-left: var(--sidebar-width-collapsed);
        }

        /* ================= TOPBAR STYLES ================= */
        .topbar {
            background: #fff;
            border-bottom: 1px solid #e9ecef;
            margin: -20px -20px 20px -20px;
            padding: 12px 25px;
            height: 60px;
            display: flex;
            align-items: center;
            justify-content: space-between;
        }

        .btn-toggle-sidebar {
            background: #f0f3f5;
            border: 1px solid #dcdfe3;
            color: #333;
            border-radius: 4px;
            padding: 6px 12px;
            cursor: pointer;
            transition: all 0.2s;
        }

        .btn-toggle-sidebar:hover {
            background: #e4e8eb;
            color: var(--accent-blue);
        }

        /* Backdrop Overlay for Mobile */
        .sidebar-backdrop {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100vw;
            height: 100vh;
            background: rgba(0, 0, 0, 0.5);
            z-index: 1040;
        }

        /* ================= DASHBOARD CARDS ================= */
        .stat-card {
            border: none;
            border-radius: 6px;
            box-shadow: 0 1px 3px rgba(0,0,0,0.08);
            transition: transform 0.2s ease;
        }

        .stat-icon {
            width: 48px;
            height: 48px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 20px;
        }

        /* ================= MEDIA QUERIES (RESPONSIVE) ================= */

        /* Tablet (Medium screens: 768px - 991px) */
        @media (min-width: 768px) and (max-width: 991.98px) {
            .sidebar {
                width: var(--sidebar-width-collapsed);
            }
            .sidebar .brand-text,
            .sidebar .nav-text,
            .sidebar .badge-count {
                display: none !important;
            }
            .sidebar .brand,
            .sidebar .nav-link {
                justify-content: center;
                padding: 16px 0;
            }
            .sidebar .nav-icon {
                margin: 0;
            }
            .sidebar .nav-item:hover .sidebar-tooltip {
                display: block;
            }
            .main-content {
                margin-left: var(--sidebar-width-collapsed);
            }
        }

        /* Mobile (< 768px) */
        @media (max-width: 767.98px) {
            .sidebar {
                left: calc(-1 * var(--sidebar-width-expanded));
                width: var(--sidebar-width-expanded) !important;
            }
            body.mobile-sidebar-open .sidebar {
                left: 0;
            }
            body.mobile-sidebar-open .sidebar-backdrop {
                display: block;
            }
            .main-content {
                margin-left: 0 !important;
                padding: 15px;
            }
            .topbar {
                padding: 10px 15px;
            }
            .topbar-title {
                font-size: 16px;
            }
            .topbar-user {
                display: none !important;
            }
        }