[Feel] Animations and explosions, Ubuntu adjustment

At the suggestion of a friend (thanks Brandon) I changed the small UFO explosions from a red to a more orange colour. Brandon's reasoning was red looks more bloody and the effect here should be fire. The change seems to fit more with the overall colour scheme of the game.

I spent a lot of time this evening playing with the colour of the asteroids. One of the things I noticed was a slight red bleed coming from the asteroids. Forum posts suggested turning off interpolation, but I found doing this made the whole game look a lot worse, so I turned interpolation back on. I passed over another post that hinted this might be fixed by using the right colours. I tried a bunch of things before passing over the post and the colours I came up with just didn't look as great as what I already came up with long ago. This is something I'm coming back to when I have a bit more time to delve into colour theory for spriting.

The "Ultimate UFO" (the round BORG-ish UFO) was reduced from 12 sprites in the animation to 8. I subtracted some lighting in various areas and shifted in others to give it some subtle lighting where there was none before. I'm thinking about making that center section a bit larger so the red scan looks a bit more dramatic.