@media screen and (max-width: 480px) {
         
     /*hide checkbox */
    #menu__toggle {
        opacity: 0;
    } 
    /* stile a button */
    .menu__btn {
        display: flex; 
        align-items: center;  /* center the content*/
        position: fixed;
        top: 20px;
        left: 20px;
        width: 26px;
        height: 26px;
        cursor: pointer;
        z-index: 1;
    }
    /* add hamburger */
    .menu__btn > span,
    .menu__btn > span::before,
    .menu__btn > span::after {
        display: block;
        position: absolute;
        width: 100%;
        height: 2px;
        background-color: #616161;
    }
    .menu__btn > span::before {
        content: '';
        top: -8px;
    }
    .menu__btn > span::after {
        content: '';
        top: 8px;
    }
    /* menu box */
    .menu__box {
        display: block;
        position: fixed;
        top: 0;
        left: -100%;
        width: 100%;
        height: 100%;
        margin: 0;
        padding: 80px 0;
        list-style: none;
        text-align: center;
        background-color: #ECEFF1;
        box-shadow: 1px 0px 6px rgba(0, 0, 0, .2);
        opacity: 0.7;
        z-index: 10;
    }
    /* elements of the menu */
    .menu__item {
        display: block;
        padding: 12px 24px;
        color: #333;
        font-family: Saira extra condensed;
        font-size: 20px;
        font-weight: 600;
        text-decoration: none;
    }
    /* open and close checkbox */
    .menu__item:hover {
        background-color: #CFD8DC;
    }
    #menu__toggle:checked ~ .menu__btn > span {
        transform: rotate(45deg);
    }
    #menu__toggle:checked ~ .menu__btn > span::before {
        top: 0;
        transform: rotate(0);
    }
    #menu__toggle:checked ~ .menu__btn > span::after {
        top: 0;
        transform: rotate(90deg);
    }
    #menu__toggle:checked ~ .menu__box {
        visibility: visible;
        left: 0;
    }
   
    /* ly */
    .menu__btn > span,
    .menu__btn > span::before,
    .menu__btn > span::after {
    transition-duration: .25s;
    }
    .menu__box {
    transition-duration: .25s;
    }
    .menu__item {
    transition-duration: .25s;
    }

}