Added a cheesy (yet strangely trippy) rotating starfield (starfield.c / .h)
Added an fps counter (bottom left)
Added powerups (one-up, hit-all, shield, rapid-fire) (powerup.c / .h)
Added a high score table (somewhat encrypted!) (hiscore.c / .h and hiscores)
Made the game run more consistently across all configurations (tweaked the game-update timer interval, which was set to run at 100fps but was only getting as many frames as your monitor could render—game should now run at 60-71.4fps)
Tweaked many physics values so the game would run as it did before (not slowed down with the framerate)
Aliens now only have one clip polygon, so they’re easier to hit
You can only shoot 4 shots at once (without rapid-fire) again
You get a completion bonus for each level
Says hit F2... at game over screen and claims to warp to each level
Aliens now taunt you, as it were
Small aliens are worth only 500 points now
Text is now drawn in front of objects where deemed appropriate
Slightly shorter time at beginning of level where player can’t be hurt
Changed how many asteroids spawn at new levels (more asteroids later)
Changed how frequently aliens spawn (more aliens at higher scores)
Removed cheats