CATACLYSM
by Jeremiah Stoddard
An adventure game written in Common Lisp

Cataclysm is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Upon startup Cataclysm reads "overworld.map" as the primary game map. A ".map"
file is a lisp file which contains data for a particular map, setting a handful
of global variables as follows:

*tileset* - This contains a string with the name of a png file containing the
            tiles used in this map. This png file will be loaded right after
            the .map file is read. This file should be 640x480, and tiles will
            be 32x32. Objects may have a transparent background. Tiles will be
            referenced by number, 0 being the tile found at 0,0; 1 being the
            tile found at 32,0; 20 being the tile found at 0,32; and so forth.

*map-width* - This contains the width of the map in number of tiles. A width of
              20, for example, would be 640 pixels wide (each tile being 32x32
              pixels).

*map-height* - This contains the height of the map as a number of tiles.

*player-x* - This contains the starting x position of the player in this map.
             This should be a pixel value: if the map is 20 tiles by 15 tiles,
             something like 320, 240 would put the player near the center. (In
             reality, this would put the upper-left corner of the player's
             sprite in the center of the map).

*player-y* - The starting y position of the player in this map, as a pixel
             value.

*floor-map* - This is an array of *map-width* by *map-height* containing
              integer values representing tiles from the map's tileset. These
              make up the ground and elements from the following variables will
              be drawn on top of it.

*wall-map* - This is an array of *map-width* by *map-height* containing
             integer values representing tiles from the map's tileset. These
             make up immobile barriers that the player cannot pass.

*obstacle-map* - This is an array of *map-width* by *map-height* containing
                 integer values representing tiles from the map's tileset.
                 These make up barriers that the player can move until they
                 reach the edge of the map, or another obstacle or barrier from
                 either this map or the *wall-map*.

*object-map* - This is an array of *map-width* by *map-height* containing
               integer values representing tiles from the map's tileset. These
               are objects that can be retrieved by the player.

*portals* - This is an array of *map-width* by *map-height* containing mainly
            empty strings. When a player walks onto a tile that corresponds to
            a non-empty string, the game will try to load a file whose name
            corresponds to that string, under the assumption that it is a .map
            file. To create an entrance to another map, set the corresponding
            string to that map's filename, and the corresponding *floor-map*
            tile to an appropriate icon (such as a door).