It's not a commercial game, blaze15. Furthermore, it's international, open-source, and not rated by any recognized review boards. Also, Tremulous has a number of mods, each of which might earn it a different rating even if it *were* to be rated as such. Tell your parent(s) there's no blood and gore, but it is a war between gun-toting Marines and vicious extraterrestrial critters so there is some animated violence (but nothing really graphic about it). I'm not one to judge what the equivalent ESRB might be, so I won't hazard a guess.