I bet many people here are at least vaguely familiar with tabletop games such as Warhammer or its 40K spinoff. Warhammer has a problem though: it's ridiculously expensive and as a result of that, doesn't have all that many players around.
So in stepped three dudes who came up with the idea of designing their own tabletop strategy game and make it available under a Creative Commons license. In practice this means (among other things) that you can download the rulebook as a PDF file for free. It also doesn't have the problem of miniatures, because you'll be building them yourself.... out of LEGO!

The rulebook includes schematics for a number of the mechas you can build, but of course you're free to design your own as well. You can also design your own terrain out of LEGO and the rule allows for destructible terrain as well, which is of course easily doable with LEGO

There's a whole forum filled with nerds who love designing stuff like this and yeah, those nerd synapses in my brain are firing like crazy right now