Query: Which company was illegally demonstrating a Nintendo game?
Context: The deal was set to be finalized and signed at the Summer Consumer Electronics Show in June 1983. However, Atari discovered at that show that its competitor Coleco was illegally demonstrating its Coleco Adam computer with Nintendo's Donkey Kong game. This violation of Atari's exclusive license with Nintendo to publish the game for its own computer systems delayed the implementation of Nintendo's game console marketing contract with Atari.