I made a Pong game for the Sega Master System (see signature) and decided to see if I could do something similar on the DS.
The code isn't very efficient, and score just doesn't exist since it wouldn't display. Not to mention cheap use of "border" objects that could have just not ever have existed.
So yeah, the crappy source is closed for those reasons, but here's the game.
EDIT! The game now is open source as v1.1, and is so much better. No more cheap object placement, score is properly displayed (albeit unlimited,) all that.