Penguin Brothers (Japan)

Penguin Brothers is a multi-screen platform game in which one or two players (either co-operatively or competitively) control a cute penguin fighting against the game's equally cute enemies. The idea is to destroy all of the on-screen enemies; once this a done, a circular key will appear; the player must pick the key up, whereupon they will be teleported to another screen which represents the second part of the stage. This screen has a silver doorway; the player must carry the key to the door - avoiding or destroying the on-screen enemies - to complete the level.