MapFetcher - press button, receive map
ArtFetcher - ^ ^, receive art

Player -> CircleCollidable
Goal -> CircleCollidable
TileWall -> Drawable; it has settings to indicate what art it should be drawing
WaveGenerator -> Drawable; has a key bound to it; when pressed, makes a Wave
Wave -> CircleCollidable; slowly grows outwards (i.e., radius increases)
ColliderWall -> Wall

Checking:
Player -> Goal, Wave, ColliderWall
