Actually destroy the player's ship.

This has been my favorite quirk of this
game the whole time I've been working
on it: when they player is shot enough
times, they don't actually die, they
just become an invincible fireball from
hell bent on revenge. And if you start
the next level after that, your ship is
still a fireball. There was a great
moment when I presented this to my
classmates in college, and I was playing
the game and talking about something
else, something relatively boring, and
then I died and I said, "Oh good, I was
hoping this would happen." Got some good
laughs from that. Good times.