document.getElementById("btn1").onmousedown = function(event) {
    if (event.button == 0) { //if (event.which == 3) {
        document.getElementById('btn1').style="background-color: #b5b5b5a1;"
        document.location.href = "next.html";





    }
    if (event.button == 2) { //if (event.which == 3) {
      document.getElementById('btn1').style="background-color: rgb(32, 33, 36);"
    }
}
