I have no comment about this particular product, its features or its author, you can read other comments if you want.

I advise the readers to check out not only Nand2Tetris but also Turing Complete game on Steam (and hopefully back on GOG at some point). The author came back to it and started posting updates a few months ago after almost 2 year silence. He rebuilt the engine with a huge performance boost and is now adding more and more features.

Not affiliated with him in any way, just think the game is great and his dedication to it deserves respect.