Alpha Version 3

Main changes:

• Added a full screen button to the game (bottom-right of the screen).
  
• Credits now de-spawn after a while if they have not been picked up.
  
• You now get some bonus credits if you pick up all the credits during a level.
  
• The action bar, warp bar and health bar now go slightly transparent if the player flies behind them.
• Fixed an issue that prevented the player from being able to use items while their cursor was hovering over the action bar.
  
• The level summary now shows an exact breakdown of how you got score in the level.
  
• Improved the store interface slightly.
• Removed some randomness in the stats of the mine and turret. Now each of those items has the same stats.