TODO

   1 Game engine:
   2         - Difficulty levels
   3         - Restart without need to relaunch
   4         - Pause
   5         - Accelerometer thread made completely separate (make it reusable)
   6                 - instead of pushing info to game: poll thread
   7         - Winding road Markov chain - add some memory to have better patterns?
   8         - Add items:
   9                 - shield?
  10         - Add enemies?
  11                 - flying: incoming
  12                 - static: laser towers
  13         - Being able to move back/forth?
  14         - Firing by tapping the screen somewhere?
  15
  16 Cairo version:
  17         - not much to do now, because it will be replaced hopefully
  18
  19 SDL version:
  20         - rewrite from scratch using Pygame
  21         - should achieve ~20fps
  22         - theming - being able to replace graphics