Planetary Defense 2012 (pd2012.atr) is a game for 8-bit ATARI computers written by Tom Hudson.
More info about the project:
http://analog.klanky.com/8bit.htm
The pd2012.atr includes a B: device handler and the game.
Since the B: handler uses SIO device $45, you need either RespeQt or SIO2BT to enjoy the URL submission of your Hi-Score.