The first halo game is honestly not a terrible game, every now and then, you will hear a swear word and there will be some blood every now and then. This is the thing, you are killing aliens, so blood is green... this is much better than the other games out there that are you killing humans. I would say around maybe 14 years old, but that matters how strict you are with game ratings and things, i believe that M for Mature rated games is 16 or 17 years and up.