Trickle (トリックル) is a cancelled maze game that was planned by Metem for Game Boy. Single player gameplay was similar to Pac Man, with players moving around a maze in a top-down view, collecting bonuses and using power ups against enemies. When playing in VS mode (against bots or other players?) the game would change its perspective in a first-person view and you could explore the maze like in Doom, trying to find and eliminate (?) your enemies.
Previews of Trickle were published in japanese gaming magazines such as Game Boy Magazine (Vol.6) and Famitsu News (August 1990), but in the end the game seems to have vanished. For sure it was an original idea for Game Boy: if you can read Japanese and see more information in the scans below, please let us know!