Platypus is a horizontally-scrolling shoot 'em up where you are flying the last ship of the F-27 Platypus fleet, and attempting to defend planet Mungola from Colossatropolis (which has become so overcrowded that its inhabitants are taking over Mungola for space and resources). The game is notable for its use of clay models for its artwork.
Although the game began as freeware, its creator, Anthony Flack, was contracted by Idigicon, a budget software publisher, to finish the game. There is some controversy over Idigicon's handling of the game. Anthony himself, while admitting that the game's rights were handed over fairly, has said that Idigicon has "contributed the least to [Platypus's] success, while profiting the most." [source:tigdb]