Apple II checkerboard

I remember years ago I wanted to see what would happen if I flipped the Apple II's hi-res pages as fast as I could.

So I did an HGR which would clear the first hi res screen, then an HGR2 to switch to the second hi res screen and filled the screen with white with a for loop. Something like HCOLOR=7:FOR I = 0 TO 191:HPLOT 0,I TO 279,I:NEXT.

Then I entered a little machine language program that would read $c053 and $c054 to flip the pages, then jump back to the top of the loop.

As I recall, it would make a neat checkerboard effect, alternating black and white down the screen. If you altered the timing of the loop, the pattern would change.

Of course, this would necessitate a reset to get out of this loop.

This is all from memory, as I haven't had a real apple II for ages.