@stefan @bit101 I think the explanation is off though. It's not that the blue bus appears to move faster/slower, it's that it appears to stop when its front enters a black stripe, because what had been a stark moving gradient line turns into a very faint gradient and so your brain goes "movement was detected but no longer; object must have stopped." When the front emerges into a white stripe again, your brain goes "oh I guess that thing is still moving, but now it's father forward" so it seems to "jump forward" at that moment. Would be cool to have a slider for the stripe widths...