:root {
            --primary-color: #4f46e5;
            --primary-hover: #4338ca;
            --bg-color: #f3f4f6;
            --card-bg: #ffffff;
            --text-main: #1f2937;
            --text-muted: #6b7280;
            --sidebar-width: 260px;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }

        body {
            background-color: var(--bg-color);
            color: var(--text-main);
            display: flex;
            min-height: 100vh;
        }

        /* --- SIDEBAR --- */
        aside {
            width: var(--sidebar-width);
            background-color: var(--card-bg);
            border-right: 1px solid #e5e7eb;
            display: flex;
            flex-direction: column;
            position: fixed;
            height: 100vh;
            z-index: 10;
        }

        .logo-area {
            padding: 1.5rem;
            font-size: 1.5rem;
            font-weight: bold;
            color: var(--primary-color);
            display: flex;
            align-items: center;
            gap: 0.5rem;
            border-bottom: 1px solid #e5e7eb;
        }

        .nav-links {
            list-style: none;
            padding: 1rem 0;
            flex-grow: 1;
        }

        .nav-links li a {
            display: flex;
            align-items: center;
            gap: 0.75rem;
            padding: 0.75rem 1.5rem;
            color: var(--text-muted);
            text-decoration: none;
            font-weight: 500;
            transition: all 0.2s ease;
        }

        .nav-links li a:hover, .nav-links li a.active {
            color: var(--primary-color);
            background-color: #eef2ff;
            border-right: 4px solid var(--primary-color);
        }

        .sub-menu {
            list-style: none;
            padding-left: 2.5rem;
            font-size: 0.9rem;
        }

        .sub-menu li a {
            padding: 0.5rem 1rem;
        }

        /* --- MAIN CONTENT --- */
        main {
            margin-left: var(--sidebar-width);
            flex-grow: 1;
            padding: 2rem;
        }

        header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 2rem;
            background: var(--card-bg);
            padding: 1rem 2rem;
            border-radius: 12px;
            box-shadow: 0 1px 3px rgba(0,0,0,0.1);
        }

        .user-profile {
            display: flex;
            align-items: center;
            gap: 0.75rem;
            font-weight: 600;
        }

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

        /* Dashboard Grid */
        .dashboard-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            gap: 1.5rem;
        }

        .card {
            background: var(--card-bg);
            padding: 1.5rem;
            border-radius: 12px;
            box-shadow: 0 1px 3px rgba(0,0,0,0.1);
            transition: transform 0.2s;
        }

        .card:hover {
            transform: translateY(-3px);
        }

        .card h3 {
            margin-bottom: 0.5rem;
            color: var(--text-main);
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .card p {
            color: var(--text-muted);
            font-size: 0.95rem;
            margin-bottom: 1.5rem;
        }

        .btn {
            display: inline-block;
            background-color: var(--primary-color);
            color: white;
            padding: 0.5rem 1rem;
            border-radius: 6px;
            text-decoration: none;
            font-weight: 500;
            font-size: 0.9rem;
            transition: background-color 0.2s;
        }

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

        /* Responsive */
        @media (max-width: 768px) {
            aside {
                width: 70px;
            }
            aside .logo-area span, aside .nav-links span, aside .sub-menu {
                display: none;
            }
            main {
                margin-left: 70px;
            }
        }