Also check http://oldcomputers.net/pet2001.html for more details.
Available for download:
You control the snake with the dotted tail, use the cursor arrows to move it up, down, left, and right - 'Q' quits. The object is to avoid hitting either your tail, or the computer opponent's tail. Whoever hits first loses. The computer snake has limited AI to avoid hitting either tail. The speed can be changed using the constant below, higher numbers = slower, the slower the easier the game becomes. Speed may vary depending on processor speed. The pet probably didn't need any delay at all because it was so slow, by todays standards. Enjoy.