header {
            position: fixed;
            top: 0;
            width: 100%;
            padding: 20px 0;
            display: flex;
            justify-content: center;
        }

        .nav {
            display: flex;
            gap: 40px;
        }

        .nav a {
            color: white;
            text-decoration: none;
            font-size: 16px;
            position: relative;
        }

        .nav a::after {
            content: "";
            position: absolute;
            width: 0;
            height: 2px;
            background: white;
            left: 0;
            bottom: -6px;
            transition: 0.3s ease;
        }

        .nav a:hover::after {
            width: 100%;
        }