Two small comments.
1) Don't check a condition, and then check the opposite condition - use Else. A lot of people toggle variables, and on the first condition, toggle to the other value, which then is evaluated immediately after, and toggles it back again. The better mechanism to use is Else, to avoid that ever happening in the first place.
2) Aztec got stuck at one point at the top, as I'm guessing he just happened to go so far past 100, that when he reversed and moved he STILL was < 100, so reversed again, causing him to jitter for quite a while. (He did eventually correct). Keep an extra variable saying which direction he is currently moving, so that can also be checked together with the location, so that condition can't happen.