This invaders game with a garden theme uses a document class to generate all game elements. You don't see your score until the end, but it's there, allowing the game to become incrementally harder as you play. After every 10 aphids squirted, it randomly generates a new, faster-moving aphid, or a new super aphid, or a ladybug (ladybugs have two different kinds of beneficial behavior which are also assigned randomly). After 50 aphids squirted, you grow a rose (meaning you gain a life), and the shooter's speed increases slightly.
For grading purposes: This game uses a scoring mechanism (I chose not to make the score visible during play because I thought it makes a nice surprise at the end!), a start screen and end screen, internal animation for the invaders, sound effects, laterally moving invaders, invaders that spawn new invaders, and a difficulty level that increases with score.