On page 63 in several places in the gray Note box, the acceleration due to gravity is written as a velocity (e.g., 9.8 meters/second) instead of as an acceleration (9.8 meters/second/second).

Also, the code doesn't really simulate a projectile in a gravity field very well... in slow motion, the ball accelerates upward from rest, rather than start at maximum upward velocity and then slow down. This is more like a model rocket, in some respects... at least one without a parachute. But it's good enough to look like it's real, and it's good enough to give me the start I need to make one that really does simulate a projectile in a gravity field (the equations are pretty simple).