Airball was initially suppose to be released for the NES back around 1990. However, for financial reasons, it was never finished and produced. The game
required a special (expensive) circuit board and Tengen figured that
this would be hard to market.
Since then, four protos have been found of the game which is actually quite a few for a game that went unreleased. Two of the four protos are nowhere near complete. The third is an estimated 70%-75%. And the fourth (scanned cart) which was recently bought off ebay (9/2006) is claimed to be around 85% making it the most complete proto of its type. In 2006, this game surfaced again on ebay as a reproduction cart, indicating that it has finally been dumped.
Airball is a Solstice-like
puzzle game that Tengen was going to release on the Nintendo. The game
had been engineered by Novotrade, the same group of people which had
done the Nintendo Impossible Mission 2 game.