So let's say I have a block of code that gets called every second. In this block of code I want to merge two circles into each other, let me illustrate: here

Every second (or 'tick') I want the red circle to move to the blue circle in order to be the exact same size as the blue circle. But, as you can see in the picture, the top-left corner has to cover a lot more distance than the bottom-right corner.

Any idea's on this?