Black Hole by Bill Eckel

Black Hole is a game based on a machine language program an my Elf II which uses the RCA 1802 Microprocessor. I understand it was originally called "Teaser." The challenge of rewriting it in Basic for the small memory could not be resisted. The program takes a little over IK of memory.

Black Hole

You are in space looking at your computer screen which shows a star surrounded by black holes.

	O O O
	O * O
	O O O

To escape you must get the pattern to be a black hole surrounded by stars.
	
	* * *
	* O *
	* * *

You can only fire at stars. The stars explode. leaving a black hole, but they also produce new stars in other locations. What the galaxy will look like after you fire at a star is important.

1 x .	x 2 x	. x 3	x . .	. x .	. . x	. . .	. . .	. . .
x x .	. . .	. x x	4 . .	x 5 x	. . 6	x x .	. . .	. x x
. . .	. . .	. . .	x . .	. x .	. . x	7 x .	x 8 x	. x 9

The number is the star fired upon. The x*s are the holes changed to stars or stars changed to holes (the reverse of what they used to be). The .*s are the star or holes that are unaffected.

For convenience sake the computer displays the star numbers in a block next to the galaxy pattern. Examples are:

O O O	1 2 3			O * O
O * O	4 5 6	Shoot star 5	* O *
O O O	7 8 9	will result in	O * O

Do not end with all black holes or you will be lost in space forever!

The lowest possible number of turns to solve the problem is eleven. There are many ways to solve it, here are two:

[REDACTED]
[REDACTED] ;-)

You cannot read the program listing and figure out how to solve it. It is very challenging game which will give hours of fascinating fun.