All you need for this game is a friend and seven counters (or coins, biscuits, matches, or whatever you like).
It's a game for two players. Place the seven counters in a pile and decide who will go first. (In the next game, the other player will have the first turn.) Each player takes turns to take away either one or two counters. The player who takes the last counter wins.
Have fun playing the game a few times.
Can you find a winning strategy, that is a way to win right from the start, no matter what move your opponent makes?