The exact level count is fuzzy, due to multiple options, but Dissent is roughly 20 levels of pure Marathon fun. Realistic architecture (well, mostly - there ARE limits to the Marathon engine), a gripping story, and very well-designed gameplay add up to a scenario that'll keep you busy for quite a while. Be sure that you don't neglect the terminals... you WILL die if you choose not to read them. A lot. More info about the story, as well as mirror sites for the download, can be found at the Dissent website. Version 1.1 fixes a bug related to the SoundEdit shuttle included with the first version (the updater, by itself, is available at the Dissent page), and a small map problem.