I kinda like http://ogame.org ... mostly because I don't really play.

The fun come from automating all the tasks that I would have to do if I was playing.

So I made this library in Go https://github.com/alaingilbert/ogame that allows you to create a bot to do everything you could do in the game.

So now, It all depends on how you want to implement the logic. (that's the fun part for me)