Every afternoon my 4 year old son has a 2 hour "rest time" in his room. He can read, play with his toys, rest, etc. It's some quality down time for all of us (my wife and I both primarily work at home).
This afternoon, when my wife went into his room to let him know that rest time was over, he has this elaborate setup sprawled all over his room; he'd created hills by spreading blankets of piles over stuff and chairs and had little miniatures all over the room.
He explained to Mom that he was playing
Military Madness.
One group of characters was supposed to be "the blue tanks" and other groups were other units found in the game.
I couldn't be more proud of him.
(P.S. - I can't wait until he's old enough to play Heroscape or Battletech, both of which are currently collecting dust in my office...)