Use left and right arrow keys to move the portal (the yellow oval) to catch the TNT. Catch the TNT. If a TNT lands on the black the score will decrease by 1. If the portal catches a TNT the score will increase by 1. If your score is 15 you win. If your score is negative 5 the city will explode and you'll lose. It's not hard. I've played it.
Have fun!
