Bugs turn to the left whenever they can. Bugs will avoid fire.
Fireballs turn left when they hit an obstacle. If they can't go left, then they'll go right. If they can't go right, then they'll turn around. Fireballs survive in fire.
Balls bounce back in the opposite direction when they hit an obstacle.
Tanks stop when they hit an obstacle. All tanks turn around whenever a blue button is pressed.
Gliders turn right when they hit an obstacle. If they can't go right, then they'll go left. If they can't go left, then they'll turn around. Gliders survive over water.
Teeth will always move towards you, unless blocked by an obstacle. If a Teeth is the same distance from you horizontally and vertically, it will move vertically first. Teeth take one step for every two steps you take.
Walkers go straight until they hit an obstacle. When a Walker hits an obstacle, it will pick a random direction and try to start moving in that direction.
Blobs just pick a random direction every time. If that direction is blocked, the Blob won't move. Blobs take one move for every two steps you take.
Paramecia turn to the right whenever they can.