Just two little typo's if anyone going back and maintaining the articles:

The line:
#define P2_Y (SCREEN_HEIGHT / 2) - (P1_H / 2)
Should be (I assume):
#define P2_Y (SCREEN_HEIGHT / 2) - (P2_H / 2)

The other is just a typo in the comments

The line:
// Player 2's paddle is a 5x50 sprite, flush left and centred vertically
Should be (I assume):
// Player 2's paddle is a 5x50 sprite, flush right and centred vertically

Keep the articles coming Josh. They're great!

Daniel
Melbourne Australia