Breathing Square Optical Illusion

This one actually is really good (as simple as it may appear)! Observe the animation on your right: behind a grid of yellow boxes there is a purple rotating square. As the square rotates, we only see the part of it not covered by the grid. It appears to grow and shrink in its roatation, as if it were breathing! Am I right?

In reality none if this is true – the square remains same in size at all times. It’s just that our brain perceives it “breathing” and changing size. Would be cool if someone could make a solution .gif file, without the yellow grid and attach it through comments… anyone? Hope you like these simple, old-school illusions the same way you like real-life ones?