Hi @DampedFred,
If valueOpacity is a number then the tween won’t work, since numbers can’t be passed by reference. You need to use an object for that.
var data = {
value: 0
};
this.app.tween(data).to({value: 1.0}, 1, pc.Linear).on(‘update’, function(){
inPocketAnimation.element.opacity = data.value;
}).start();