It's an optical illusion caused by how the cube is angled downwards and away from the viewer.

I know it can't be shrinking but my brain still thinks it is

Wut...

I see what you mean, but the illusion doesn't work on me, all I see is the bottom part of cube, then as I scroll up, I see more of the cube, its like this, I dont see it as shrinking or growing, just being partly covered, or fully uncovered. Yes I'm weird I know

[image deleted]WOAH