The best definition I've seen for what constitutes a game is this: A game is an experience created by rules.
That captures what distinguishes a game (as an artform) from other media. You could throw in some qualifiers to perhaps narrow it down (is paying your taxes a a game?) but it's not really necessary.
The goal we were given at the start of the summer was just to create a tech demo, the team tried to make a game out of it as much as possible though. The original plan was to release a tech demo at the end of the summer and then make a game with it after, the after part hasn't started yet though, and I'm not sure if it will.
That captures what distinguishes a game (as an artform) from other media. You could throw in some qualifiers to perhaps narrow it down (is paying your taxes a a game?) but it's not really necessary.