4 by Jojoisjo (2001)

Four is an engine showcase game. The engine is meant to be used with the mouse interface, which is pretty rare in zzt. The goal is to achieve something of a point and click adventure thing. Reading the pretty critical reviews I expected a very barebones demo. But that wasn't the case: this game tries to be a game. And it's not as bad as others say in my opinon. The graphics are slightly lacking, partly due to engine limitations. The story is ok, however the ending, where the not-great concept of the game gets explained through straight exposition, is a bit disappointing. The mechanics are the good old item gameplay.
I don't really see how this is significantly worse than other zzt games. The setting, the graphics and the puzzles were acceptible. It's not outstanding but it's ok.

Now, what about the engine? Well, it poses substantial limitations to the board design and graphics. However it presents an interesting alternative to default zzt movement, and in my opinon it has some solid advantages. First of all, the cursor is free to move everywhere (except into interactive objects). This freedom is great, as I've often felt uncomfortable in moving around walls in zzt. Also, because changing boards happens through movement through doors close together, that's pretty quick (especially backtracking). I've found moving is easier in this environment, while still allowing to interact with objects. Additionally it (usually) makes it very clear what exactly you can/have to interact with.

So, are the limitations worth it? I can't really tell. As for this game, it's fine but not exceptional. So:

Verdict: Not really recommended unless you are curious to try out the engine