.header-button{
                color: black;
                font-size: 16px;
                cursor: pointer;
                position: relative;
     }

            .header-button::after {
                content: '';
                position: absolute;
                height: 2px;
                left: 0;
                bottom: 0;
                width: 0;
                background-color: purple;
                transition: width 0.4s;
            }
            .header-button:hover::after {
                width: 100%;
                opacity: 1;
            }