I'm polishing my gameplay and have some difficulties with this one. I don't know if it's possible to animate the alpha parameters of an object. I want to create a secret room, masked by a wall. When the player approach/touch this wall it becomes invisible. And when he leaves the room the wall become again visible.
One way would be to change the X or Y value of the wall so that it "moves" off screen when you approach it. In conjunction with this, you can have a second version that you set the opacity to low underneath the first one. That way the wall would look as if it is still there but semi transparent. The second version would be set to decoration.
Thanks @jerry That’s a good idea, but how to do it, and also how to make it visible again when the player leave the secret room?