When I start teaching my game design students, one of the questions that I'll often hear is "What is a game?". Now, to some people, the card game War (http://en.wikipedia.org/wiki/War_(card_game)) is a game; however, the game is already determined before anyone actually plays the game since players have absolutely no interactions besides flipping cards.

Renowned game programmer and designer Sid Meier says that a game is "a series of interesting choices," and I really like that definition. At my alma mater and current employer DigiPen, we were taught that a video game was a real-time interactive simulation.

Having an environment is an excellent first step towards creating your game project; but, without anything to do but look around, this is a real-time simulation but it's not very interactive.