Many titles are clones of popular games from the era ("Tetris", "Bomberman", "Lode Runner", "Battle City", etc.). Bit Corp. (and later UMC) is given sole credit within each game, but inconsistencies in game content and labeling make it far more likely that several developers were involved in designing individual games; two external developers are currently known, Gamtec and Hengmao Electronics. Some titles suffer from assorted bugs. A few titles seem to be original concepts, and a great many more remain mysterious due to their scarcity.