The purpose in Citadels is to build a citadel. Sounds simple enough. To do so, you're going to have to get your peasant servants to work by gathering resources, building various types of buildings, and manning them when necessary. Still sounds pretty straightforward so far.
The "only" problem is the game is so ridden with bugs and glitches that the most simple tasks become impossible. Peasants getting trapped between buildings, path-finding issues, animation bugs, and self-destroying castles are just some of the problems.
And if that weren't enough, the game is full of some design decisions that just make you think "WTF." We're talking catapults with faster movement speeds than foot solders or the absence of the option to "Load Game." Then again, it's not possible to save a game either, so I guess that cancels itself out.
Released in 2013, it received a "Very Negative" score, and you can pick the monstrosity up for just 14,99€. I'd bother doing that conversion rate into US dollars, but if you're actually considering buying it in the first place, chances are you don't care about your money anyways.