TODO:
- use t<0 for collision detection
- move to free space when collision unavoidavle (multiple colisions in short time)
- thrust when min. object distance too low in next x frames
- shoot only if object will be in range on hit
- goto next object when fired (ignore it for some time)

v021:
- hyperspace depending on velocity of ship and object

v020:
- replaced square distances by true distances

v019:
- shoot only small asteroids, when number of asteroids reached maximum and no collisions

v018:
- fixed state when stats disabled

v017:
- added GUI

v016:
- shoot when prev. frame not shot

v015:
- shoot when rotating to desired direction and another object can be destroyed

v014:
- added tracking for ship and saucer based on history
- move to screen center when level finishd

v013:
- fixed tracked speed update

v012:
- update tracked speed on new observations
  (use overall tracked positions for velocity estimation)

v011:
- ADDED: shot angle restriction depending on object size and distance

v010:
- ADDED: shoot close objects in specified time frame
- FIXED: colliding objects may be chosen in wrong order

v009:
- ADDED: shoot saucer before other objects when in range

v008:
- ADDED: shoot colliding objects first

v007:
- FIXED: shoot angle

v006:
- ADDED: score, lifes and state detection
- ADDED: 5 minutes limit

v005:
- ADDED: collision detection of shots
- ADDED: use tracking for collision detection

v004:
- CHANGED: shoot only when object is in target range
- CHANGED: if nearest object is tracked, turn ship considering the objects and the shot velocity
- FIXED: tracking

v003:
- ADDED: tracking for objects

v002:
- ADDED: asteroid tracking implemented
- FIXED: dont thrust when no objects

v001:
- started
