Being said roommate, let me give a quick rundown on how Bangai-O works:

-You fly around freely in all directions with the D-pad, using the face buttons like a second D-pad to fire in all directions.
-You have two weapons, a homing missile and a bouncing laser.
-Enemies fire shots at you while you are doing so. If your shots collide withe enemy shots, they destroy each other.
-By pressing R, you can fire a ring of missiles in all directions. Under normal circumstances, this shoots 40 missiles. You have a limited stock of this attack, which is replenished by causing explosions.
-The more enemy bullets there are close to your mech when you use this attack, the more missiles it fires, to a maximum of 400.

Those last two points are the important ones. Together, during a sufficiently frantic situation, you can essentially hammer on the special attack button, firing hundreds of missiles every second, and never run out. The game is basically the greatest adrenaline rush in gaming history.

The DS sequel seems to have more than just the two weapons, and also some kind of melee attack. I'm so excited for this that it's going to take all my willpower to only buy it once.

EDIT: Oh yeah, the space fruit. Whenever anything explodes, it drops a fruit. The more explosions were on-screen when it exploded, the higher-scoring of a fruit it drops. The best are watermelons.