An air hockey table on your phone

Lay the phone between two players. Each finger is tied to the half of the screen where it first touched, so both players can play at once without getting in each other’s way. The puck bounces off the walls and flies faster when you hit it on the move, because the mallet’s speed pushes the puck. A little friction slowly slows it down. The top player’s score is drawn upside down so it reads correctly from across the table.