I don't understand the fullscreen stuff

Not sure how to make something fullscreen using this code.

FullScreenMobile.prototype.update = function(dt) {
    if(this.app.mouse.wasPressed(pc.MOUSEBUTTON_LEFT) && !fullscreenOn){
        fullscreenOn = true;
    } else if(this.app.mouse.wasPressed(pc.MOUSEBUTTON_LEFT) && fullscreenOn){
        fullscreenOn = false;
        console.log('not fullscreened');

I looked at the tutorial, but not sure what I’m missing. Can someone explain the simple set up for me.

Which mobile browser are you using ? As the enableFullscreen is implemented by the Element.requestFullscreen API, if your browser do not support it, it won’t work. You can go HERE to see the current stage of Fullscreen API: