The collider on the screen shouldn't change. You may have a bigger screen size, but since you are not using it (you're using the manual setting on the root), it is completely irrelevant. The button should stay the same size proportionally. Does your button's size change? If your button is 200x30, it should still be 200x30 after the atlas swap. The whole point of the atlas swapping is to handle doubling (or halving) of resolutions, iOS style.