When Steven was just itty-bitty he invented a game that we still play, and is surprisingly fun and challenging.
He named it the Up and Down game.
He would stand at the top of our stairway and someone else would stand at the bottom, and we'd start pitching and catching. Every time the person at the bottom of the stairs catches the ball they get to move up one step and once they reach the top the game is over and they won. If they miss they have to go down to the bottom and start over.
Up and down, up and down we'd go. Getting to the top is surprisingly difficult especially if the person on top is trying to get the ball past you.
I can't begin to count how often we've played this game invented by a two almost three year old. It's still a favorite!