Concentrate! is a Coco 3 only version of the classic memory game, where you flip two tiles trying to find a match. You compete with a second player, so if you uncover two non-matching tiles, the other player has the opportunity to find the other match (as long as they remember where you found the other match). This was a magazine game, although it's author, Eric Wolf, also did many commercial games for the Coco. The game allows the players themselves to select their input device, and they can share the same one (as they take turns irregardless), including both joysticks and/or the keyboard.
Title: Concentrate!
Author: Eric A. Wolf
Publisher: Rainbow Magazine February 1990
Released: 1990
Requires: Color Computer 3, 128K RAM, cassette or disk, joystick optional.