Don't forget - due to the speed of light it takes 5-10 hours to get feedback on if the square illuminated, but maybe more because you don't know exactly how long you'll need to wait.

And there's uncertainty in whether your measurement is accurate.

And there's a background of other illuminated squares that can interfere with your readings.

And you're spinning while this is going on.

And the target square is continually moving. You might have just missed it.