I'm shocked nobody's mentioned the Interactive Fiction Database, which is loaded up with tons of these available for free as abandonware or FOSS, depending on when it was created.

Here's my favorite, Conterfeit Monkey:

https://ifdb.org/viewgame?id=aearuuxv83plclpl

It takes unique advantage of the text-based format by allowing the player to add and remove letters from words to transform any noun into any other noun if it can be done with a single letter change.