As of now our program has 4 main classes. The game.py class constructs the screen, constructs players/enemies in a group, and calls group.update/group.draw. We're implementing the "leftover interval" update scheme, where we have a global "frame-time" variable that keeps track of all the time that must be spent updating, and from which "interval-length" intervals are subtracted.
Unit.py is the class from which Player and Enemy will inherit. The purpose of this class is to keep track of a player/enemy in the screen, and have special methods, to be implemented in subclasses, for when the player/enemy hits the border of the screen. For instance, the player class plays audio every time the player touches the edge of the screen, and the enemy class changes one component, horizontal or vertical, of its vector, so that it bounces.