Optimise explosions

[Kroc]

Explosions cause major chug. They appear to be essentially a bunch of space 'dust', the same as the star-field in the background. I'm not sure what to do but optimising the star-field handling will probably go a long way, but the explosions themselves will need to be looked at -- reduce particle count?

[Kroc]

Some suggestions:

• Render the explosion into a sprite? (limits size)
• Separate the explosion from the regular dust, and transform it in 2D only; I.e. the dust particles do not spread in the Z-direction. Could also be rendered to a buffer, like the sprite option