Indeed, Chessie is yet another chess program. However, it is special in that it fulfills a need other programs don't address well: the need for a very intuitive chess opponent, who does not allow you cheating, e.g. taking move back, removes the opportunity for misclicks, plays at many different, easy levels, but strong levels as well, etc.
We built Chessie as we needed a chess opponent for our kids, who were learning chess. We did not want a program that shows your level in the game, allows changing things during the game, like the level, the side, the clock, etc.; in short, we wanted a program that simulates a real player playing in a real game. We also wanted to have several levels for beginners (it now includes 5 levels dedicated to simulate kids playing style!) and a user interface that is suited for children. Finally, we wanted to record all games played so we could analyse them after the fact.