Version 0.2

Added a series of new enemies and some other general improvements.

Changelog:
New enemies:
Knife: fast enemy, but dies in one hit.
Orbiter: The first medium size enemy, tries to orbit the player and shoot them with a heavy cannon.
Reaver: Heavy enemy that is fast for it's size class and spawns knives when it dies.

Slightly reworked the Goliath, it now shoots in a spread and is much less messily set up behind the scenes.

Gave enemies an afterburner so they speed up when the player is too far away.

Added two new explosion effects

Improved the look of the scoreboard and added a UI piece to when you exit the game before dying.

Known issues:
Score shows up twice when dying regularly.