******************************
 Laser Chess documentation
 (c) 1997-2002 by Eric Tucker
******************************


ORIGINS
=======

Laser Chess first appeared on the Atari 1040ST in the late 1980's.
It was the winner of a programming contest in the April 1987 issue of
Compute's Atari ST, and was written by Mike Duppong.


OVERVIEW
========

Laser Chess is like chess in that the game is played on a grid
(though 9x9 instead of 8x8), each side controls two rows of pieces,
and that the object is to capture the opponent's king.

But there's an exciting new piece: the LASER!  Each side has one
laser, which can fire a beam which has one of four interactions with
pieces it hits, depending on the type and orientation of the piece.
It can be deflected to another direction, it can destroy the piece, it
can pass straight through with no effect, or it can be absorbed
completely.  You can tell by looking at the shading on the edge
exposed to the beam what effect will occur:

	- BRIGHT edges deflect laser beams.  If a beam hits the edge
	  it will bounce off at the appropriate angle as dictated by
	  physical laws.

	- DIM edges are vulnerable to laser beams.  If a beam hits the
	  edge the piece will be destroyed (and the beam will go no
	  further).

	- DOTTED edges are indifferent to laser beams.  If a beam hits
	  the edge it will go straight through as if the piece were not
	  there.

	- Beams are absorbed if they hit the edge of the board.

There are two exceptions to these rules which are explained below.

Unlike in chess, only certain pieces can capture other pieces by
moving onto them.  Also unlike in chess, all pieces have the same
rules governing their movement.  Aside from whether they can capture
other pieces, the main way pieces are differentiated is in how they
react to laser beams.


TYPES OF PIECES
===============

There are eight kinds of pieces in Laser Chess.  Four of them are
"aggressive", meaning that they can act directly on other pieces.

	- THE KING (who looks like a diamond with a crosshair in the
	  middle) is vulnerable to lasers on all sides, and can capture
	  other pieces by moving onto them.

	- THE LASER (which looks like a thumb tack) is vulnerable to 
	  laser beams on all sides, and can fire laser beams out of
	  its pointy end.  Lasers can "destroy" other pieces, which is
	  effectively the same as "capturing" them; the piece is gone 
	  from the board, never to return for that game.

	- THE HYPERCUBE (which is a square drawn with dim dotted lines)
	  is "laser indifferent": beams will go through it with no effect
	  on either it or the laser.  If a hypercube moves onto another
	  piece, that piece will be teleported to a random unoccupied
	  square on the board, and oriented in a random direction.
	  (Note that this does NOT occur if someone else tries to move
	  onto the hypercube.)

	- SQUARES have one reflective side and three vulnerable sides.
	  They are standard, reflective geometric shapes like the four
	  passive pieces below, except for one thing: like the king,
	  they can capture other pieces by moving onto them.  Because
	  their edges are flat (rather than diagonal, as with some pieces
	  described below), a beam hitting the reflective side will be
	  bounced right back where it came from, destroying the
	  originating laser.

Each of these four kinds of pieces is only allowed to assault once
once per turn.  For example, if a particular square captures a piece
in the first move of a turn, that same square cannot capture any more
pieces that turn.  Other squares, the hypercube, or the king could
still move onto other pieces, and the original square could capture
again starting next turn.  Likewise, the laser can only be fired once
per turn.

The remaining four pieces are "passive", meaning that they cannot
directly act on other pieces: they can only move, rotate, and sit
around waiting for lasers to destroy or bounce off them.

	- TRIANGLES are isosceles right triangles whose vertices are all
	  on corners of the square containing them.  The hypotenuse is
	  reflective, and the other two sides are vulnerable.  They can
	  be oriented in any of four directions.

	- THE BEAM SPLITTER is also an isosceles right triangle, except
	  that the two equal sides are reflective, while the third is
	  vulnerable.  The orientation is different, too: the vertex
	  where the two equal sides meet is in the middle of the square.
	  If this vertex is struck head-on by a laser, the beam is split.
	  For example, if a beam splitter is "pointed" north, these are
	  the effects of laser beams hitting it from each of the four
	  directions:
		- From the North: beam splits and heads both East and West.
		- From the West: beam deflects to the North.
		- From the East: beam deflects to the North.
		- From the South: beam splitter is destroyed.

	- DIAGONAL MIRRORS are straight lines that are reflective on all
	  sides (and can thus never be destroyed by a laser).  They will
	  always remain diagonal: the only two orientations permitted are
	  NW-to-SE and SW-to-NE.

	- AXIS-ALIGNED MIRRORS are constrained to be parallel to either
	  the X or Y axis.  Thus, they can face North-South or East-West.
	  A beam striking such a mirror head-on will be reflected back,
	  destroying the laser.  A beam striking the mirror from the side
	  will pass through with no effect.


THE NEUTRAL HYPERCUBE
=====================

In the center of the board is a stationary hypercube that is not owned
by either side.  If any piece moves onto it, that piece will be
transported to a random spot on the board and oriented in a random
direction, exactly as if a player-owned hypercube had moved onto it.
Note that this applies even to kings, hypercubes, and squares -- they
cannot capture or teleport the neutral hypercube.

The neutral hypercube is also the one exception to the rule that laser
beams are not affected by dotted lines.  The neutral hypercube will
absorb any laser that enters it, without being affected itself.


EXCEPTIONS TO THE LASER EFFECT RULES
====================================

We have now covered the two exceptions to the rules of laser effects 
listed in the introduction.  To make sure you caught them, they are:

	- If a laser hits an axis-aligned mirror which is pointed in
	  the same direction the laser is headed, there is no interaction,
	  even thoguh the surface looks reflective.

	- Lasers are absorbed by the neutral hypercube, even though
	  its surface looks laser-indifferent.


PLAYER TURNS AND MOVING PIECES
==============================

As with any game of this genre, players alternate turns.  However, in
Laser Chess, each player is allowed TWO actions per turn.  There are
three kinds of actions allowed:

	- Firing a laser.  This costs one action.

	- Rotating a piece.  This costs one action, no matter how many
	  degrees you rotate it; but once you drop a piece after having
	  rotated it, picking it up again to rotate it some more would
	  cost an additional action.

	- Moving a piece.  This costs one action per move in any of the
	  primary four directions.  A piece cannot jump over other pieces.
	  Thus, diagonal moves are possible, at a cost of two actions,
	  only if the way is not blocked.


TIME LIMITS
===========

If you are playing with time limits (see INSTALL.txt for how to set
this up), two vertical bars will be shown on the left and right sides
of the screen.  Each one corresponds to one of the teams playing the
game, according to the color of the bar.

If the time limits are per-turn, only the bar of the team whose turn
it is has any meaning, and it shows the percentage of time that
remains for that turn.

If the time limits are per-game, each bar represents how much total
time left the corresponding team has to make moves in that game.

In either case, a text display in the upper right provides a digital
readout of time left.


ENDING THE GAME
===============

If a king is captured or destroyed, the other side immediately wins.
If both kings are catured or destroyed simultaneously (which can be
done with a beam splitter), then it is a stalemate.


USER INTERFACE
==============

You can play entirely with the keyboard, entirely with the mouse, or
any mixture that suits your fancy.

The important keystrokes to know are these:

	- Arrow keys move the cursor.

	- Enter picks up or puts down the piece under the cursor.

	- The space bar rotates a piece that you have picked up.

	- The 'F' key fires a laser that you have picked up.  Press and
	  hold the 'F' key to see the path that the laser took, and the
	  pieces (highlighted in yellow) that the laser will destroy,
	  if any.  When you release the 'F' key, the beam will go away
	  and any destroyed pieces will explode.

	- Escape puts down a piece that you have picked up, leaving it
	  exactly as it was.

	- 'P' pauses the game, or resumes a paused game.  In a networked
	  game, only the player whose turn it is can pause or resume.

With the mouse, you can pick up or put down a piece by double clicking,
and move the cursor by single clicking.  To fire your laser (provided
that you have the laser picked up) or rotate any piece, you can use
the buttons at the bottom of the screen, or the menu items at the top.


CONTACTING THE AUTHOR
=====================

You can reach me at erictucker2000@yahoo.com if you have questions,
comments, bug reports, or whatever.

Enjoy!
