Keep of the Mad Wizard is a single-player text-based RPG of the dungeon crawl variety, with randomized elements. It comes in a gamebook-like format, and can be played online or offline.
The game is meant to be replayable. It's a coffeebreak game that can be completed in about 10 minutes once you are familiar with it. But each time you'll get a different challenge, so pay attention to your resources! (See the built-in help for how to play.)