strange. Logically the test above should NEVER jump as it's moving whole pixel numbers once per frame so it should be totally smooth UNLESS some background task causes it to miss a frame. Of course using fixed rate logic/delta time or tweening should mean that when a frame is missed, the code compensates by moving the object the correct distance based on time passed, but this shoudl still result in a visual jerk. It's interesting that the tweening has resulted in no jerks on your PC. Wonder if you can adapt the square test above to use tweening...