A space invaders game that I'm teaching myself pygame with, and that I'd like to customize extensively:

• levels (increasing speed, number of enemies, accuracy of enemy bombs...)
• tiers of enemies with different scores
• music and sound effects
• explosion sprites
• enemies speeding up as the move closer
• enemies having two states to imitate movement
• enemies shooting/dropping bombs
• fly-across enemies for bonus points
• player lives
• custom enemies that add temporary game features
  • speeding up/slowing down
  • tilting the screen (?)
  • special ammo
  • same-color enemies all drop dead at once
  • multiple player spaceships
  • arkanoid instead of laser shot

I'd also like to use this to learn Kivy, and port this to a mobile game.