style.css

body {
    margin: 0px;
}

h1 {
    margin-block-start: 0px;
    margin-block-end: 0px;
    text-align: center;
    font-size: 100px;
    padding: 1%;
}

h2 {
    font-size: 30px;
}

#encryptorMain {
    margin-left: 20%;
    margin-right: 20%;
    margin-top: 3%;
}

#shift, #word {
    height: 20px;
    width: 100px;
    text-align: right;
    font-size: 15px;
    position: relative;
    bottom: 6.5px;
}

#word {
    font-size: 20px;
}

textarea {
    width: 100%;
    font-size: 20px;
}

main button {
    position: relative;
    top: 90px;
    width: 20%;
    left: 5%;
    margin: 5%;
    padding: 5%;
    text-align: center;
    font-size: 25px;
}

header button {
    float: right;
    position: absolute;
    top: 14px;
    width: 20%;
    right: 3%;
    padding: 3%;
    font-size: 25px;
}


header {
    background-color: dodgerblue;
}

@media (min-width: 1025px) {
    main button {
        float: left;
    }
}

@media (max-width: 1024px) {
    main button {
        background-color: auto;
    }
}

@media (max-width: 980px) {
    h1 {
        padding: 5%;
    }
    
    h2 {
        font-size: 47px;
    }

    main button{
        top: 95px;
        width: 80%;
        height: 200px;
        left: 5%;
        font-size: 50px;
    }

    header button {
        font-size: 50px;
        width: 30%;
        height: 120px;
        top: 49px;
        right: 7%;
    }

    #encryptorMain {
        margin-left: 5%;
        margin-right: 5%;
        margin-top: 3%;
    }

    textarea {
        width: 100%;
        height: 8em;
        font-size: 35px;
    }

    #shift, #word {
        height: 25px;
        bottom: 10px;
        font-size: 35px;
    }

}