Tonight after a fun but late evening, Lukasz asked me what 60x60 is. I explained to him how to figure out 6x6 first and then use the zeroes to get to the right number. Then he asked what 3,600x2 is, so I walked him through that, too. Then he exclaimed, "it's 7,200 seconds past bedtime!"... and at 10:30 p.m., yes, yes it was.