bullets lose strength over time and when hitting something
moved sounds and images to new directories
refactored creation of upgrades
asteroids don't get spawned at the position of the player
jumping to the next level is now possible
limited max amount of bullets to 11
moved playercentric code into its own file
added particles
they are created when an asteroid is destroyed
moved class Game to game.dart
modified behavior when leaving level
AutoPilot takes control once player wants to leave the level
switching levels now with effects
made level leaving effect more.. juicy
hyperspace effects don't start immediately
refactored BackgroundRenderSystem into NormalSpaceBackgroundRenderSystem, HyperSpaceBackgroundRenderSystem and BackgroundStarsRenderingSystem
added HyperDrive, player starts level by leaving hyperspace
minor refactoring, preparations for hyperspace sound
better particle effects
modified generation of random velocity
made using the hack to workaround missing literal types easier
using a map to remember pressed keys
fixed bug when leaving hyperspace
made hyperspace mode look better