function on() {
    document.getElementById("player").className = "player_aktiv";
    document.getElementById("button_on").className = "button_on_none";
    document.getElementById("button_off").className = "button_off";
}

function off() {
    document.getElementById("player").className = "player_inaktiv";
    document.getElementById("button_off").className = "button_off_none";
    document.getElementById("button_on").className = "button_on";
}