

This  is a Prolog  implementation of  Columns - a variant  of Tetris -
where  pieces  are  columns  of  tree  symbols   whose  order  can  be
changed by rotation (the column itself is not rotated, unlike Tetris).

The game takes place in a  rectangle and the columns appear in the top
of the  rectangle  and "fall" slowly  until they hit  the bottom.  The
player  can "steer" the  column, "rotate" the  symbols and  "drop" the
column when none of the previous actions is necessary.

When a column  hits the bottom if there is a sequence  of tree or more
equal symbols  in  the horizontal,  vertical  or diagonal  then  those
symbols will  be removed and the symbols  placed above will "fall". If
as result  of this movement  new  sequences have been formed then this
last operation will be repeated.

The game  consists in  placing a  random series of  columns trying  to
remove  the largest number of  symbols  possible.  It  ends  when  the
rectangle is filled with symbols.  

The key assigned is the following:

	<j>	<k>	<l>		<SPACE>
	left	rotate	right		drop
	

*notes*

You may have to compile the random.c for you machine. The file
random.o in the distribution was compiled for a sun4.

The  "speed"  of  Columns  depends  on  the Prolog engine  and on  the
machine running it.  The  predicate   'speed/1'   should  be   changed
to each particular case.
