SpaceGate: Procedural survival mode

I have integrated a new survival mode where the player must defeat wave after wave of randomly generated aliens!

Firing is 4-way (like in the games Robotron or Gamma Bros) and is auto as in arcade mode.

New controls:

Control type A: Arrows to move, WASD to aim
Control type B: Mouse to move, arrows to aim

I hope that once it's complete in the next few days that it will encourage some skills and require some replay!