Today I had the idea of, well, um... what do you think?
Get some plastic, and cut 4 sheets of them toilet shaped. Draw red bulls eyes in each one. lable one, 10 points, one 20 points, one 50 points and one 100 points.
Put the 10 point toilet on the ground, in the corner, where they usually go.
Put the 20 point toilet about three feet up. The 50 point toilet about six feet up.
and the 100 point toilet about 8 feet streight up in the air, so they have to aim UP to hit it.