File: blackbox.el.html

by F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu> doc comment by Root Boy Jim <rbj@dsys.icst.nbs.gov>, 27 Apr 89 interface improvements by ESR, Dec 5 1991.

The object of the game is to find four hidden balls by shooting rays into the black box. There are four possibilities: 1) the ray will pass thru the box undisturbed, 2) it will hit a ball and be absorbed,
3) it will be deflected and exit the box, or 4) be deflected immediately,
not even being allowed entry into the box.

The strange part is the method of deflection. It seems that rays will not pass next to a ball, and change direction at right angles to avoid it.

                             R 3
1 - - - - - - - - 1
- - - - - - - -
- O - - - - - - 3
2 - - - - O - O -
4 - - - - - - - -
5 - - - - - - - - 5
- - - - - - - - R
H - - - - - - - O
2 H 4 H

Rays which enter and exit are numbered. You can see that rays 1 & 5 pass thru the box undisturbed. Ray 2 is deflected by the northwesternmost ball. Likewise rays 3 and 4. Rays which hit balls and are absorbed are marked with H. The bottom of the left and the right of the bottom hit the southeastern ball directly. Rays may also hit balls after being reflected. Consider the H on the bottom next to the 4. It bounces off the NW-ern most ball and hits the central ball. A ray shot from above the right side 5 would hit the SE-ern most ball. The R beneath the 5 is because the ball is returned instantly. It is not allowed into the box if it would reflect immediately. The R on the top is a more leisurely return. Both central balls would tend to deflect it east or west, but it cannot go either way, so it just retreats.

At the end of the game, if you've placed guesses for as many balls as there are in the box, the true board position will be revealed. Each x is an incorrect guess of yours; o is the true location of a ball.

Defined variables (10)

Defined functions (17)

Defined faces (0)