The game takes place in Crystalworld, a world made up entirely of crystals, most of which can be made
to go up in a satisfying explosion. It also contains evolving,
self-organizing entities (henceforth referred to as monsters), whose disposition towards you is less
than friendly. When the game is started, they immediately begin moving around, assembling themselves into
groups hunting for you. They act in a lifelike fashion because they are true implementations of artificial
life technology, and do not cheat in any way. They have no knowledge of your whereabouts unless they see you,
and they cannot see what is behind them - in other words, if you see the backside of a monster's energy-indicator, or there is
a crystal in the line of sight between a monster and yourself, then that monster does not know your location.
It is, however, constantly communicating with its fellow monsters, and will gain indirect information about you
if other monsters see you or you kill a monster or attack a boss. The way the monsters use such information can
be used to manipulate their behavior, and a good player of this game will have to observe how the monsters react
to his doings and learn to lead them into traps and split their groups.
Monsters have a health-indicator that sits on top of them, and an energy-indicator that comes out sideways. When the health indicator goes all the way down, the monster explodes and dies, and when the energy indicator goes all the way down, the monster is out of energy and cannot heal itself or shoot any more. A health indicator of a different color is the mark of a health boss, who gives extra healing to monsters in its vicinity and can get their health to 200 instead of the normal 100. Energy bosses do the same for the energy of their followers. Energy above 100 does not register on the energy-indicator, however. There are also fertility bosses, who help the monsters in making babies, and who can only be recognized by their slightly different body color.
Players can set down new crystals and destroy existing ones, thereby changing the geography of the rooms, which influences the behavior of the monsters. It is possible to make rows of crystals with the gaps sized so that small monsters and players can pass through, but large monsters are held back. The entrance to a room can be changed so that monsters will not normally find their way out, as in a lobster trap. The monsters themselves will at times become agitated and shoot at crystals in order to break through a wall and reach a location where they hear the cries of their brethren. Our game is the first shooter game where the geography is totally changeable and its manipulation is an important part of advanced strategy.
When enough monsters come together in one area, and they have enough energy, they will make a baby monster. A group that is large enough and left alone will make one baby after another until the player is overwhelmed by sheer numbers. When the player gets the message that the monsters have made a baby, it is imperative to immediately engage this group of monsters (the location of a birth is given away by a special explosion cloud rising high into the heavens) and split it in two, leading one of the subgroups far away from the other. During the game it often makes sense to leave a small group of monsters wandering around in a remote corner and to attack a larger group, because if all stragglers are killed the remaining group will normally start making babies.
The game consists of six arenas, with play in the later arenas becoming more difficult. In arena 3 the player's ally, Selene, is held captive inside a crystal tower. After the player has destroyed this tower she will emerge and join in the fight against the monsters. It is advisable to keep her in sight or close by at all times, unless one of the fighters must rest and rebuild energy in a secluded spot. Playing with Selene by one's side is quite involved and challenging. Selene is represented as a geometric object floating in the air, but she is really a very beautiful woman. Just use your imagination.
The damage done by projectiles in this game is proportional to (speed x weight). Speed goes down with distance traveled, so that a shot fired at a distance does much less damage than up close. Monsters will not fire if you are too far away. Projectiles fired by monsters can hit and injure other monsters, so monsters will generally refrain from firing if a monster is in their line of fire. When a projectile hits the player, he is pushed around by it and tossed in the air.
All explosions in the game damage all objects that are close by, so if you go nose to nose with a monster that is out of energy and massacre it, you will take serious damage from your own exploding projectiles. When you fire into a group of monsters, you not only damage the one you hit but also all who are close by. Destructible crystals loose their primary color when they are hit, and explode when it is all gone. Crystals set by the player with F6 have very little primary color and can usually be exploded with one hit. The damage done by exploding crystals is proportional to the amount of secondary color they contain, and crystals set by the player with F6 have lots of this color and explode with great force, so they are well suited for use as bombs.
When the player is invisible(the message "INVISIBLE" is displayed near the top of the screen), he has the power to herd monsters - those in his vicinity will tend to go in the direction he is facing. If the player finds a section of destructible crystals at the edge of the world (hint: arena 6), he can open the door to the abyss by destroying them, lure a large group of monsters into the vicinity, and then herd them into the abyss where they fall to their death. This is a tricky maneuver, because the invisible player can still be hit by projectiles, and every hit shoves him around, so the player may well fall to his death himself.
When levitating, a player cannot be hit by the low-flying projectiles. However, the monsters are too stupid to notice he is up there and keep shooting, possibly hitting each other. Gaining height in levitation consumes 10 times as much energy per second as staying aloft. Levitation was put into the game primarily as a way for the player to escape when he is surrounded by monsters, a very frustrating situation where one otherwise would suffer a slow and certain death.
Invisibility time and crystals are found in one type of powerup, health and energy in another, and documents in still another type (you should not find any documents in the executable version - if you go into the source code you can enable documents, but those that show up are just there for testing of the story engine). Monsters will try to pick up any powerup that is in the open, and when their health/energy is low, they will use part or all of a health/energy powerup upon picking it up. It is a help if you can get these powerups first.
Players can heal by converting energy into health, and monsters do this automatically at a genetically set rate. Energy is the only resource in the game and must be managed wisely. A player who starts with 500 energy (you can start with up to 1000 by carrying an excess over from the previous arena) has 108 seconds of continuous shooting time, and after that his energy replenishes at a rate that allows him to shoot a third of the time (assuming he does not use energy to heal or levitate). The speed at which the monsters regenerate their energy is determined by the difficulty level, which is automatically adjusted after every arena, or can be set from the entrance menu. The game was initially balanced at a difficulty level of 100 using basic uninspired gameplay - subsequently every arena has been beaten and the game rebalanced at a difficulty level of 170, which requires knowledge of the arenas, sophisticated gameplay, and a willingness to loose if luck turns against you. At a level of zero, the monsters do not regenerate their energy at all, and are very easy to beat, especially if there are no energy bosses around. The really low numbers are the equivalent of using a cheat code, levels around 30 are appropriate for novice gamers who have never played a shooter before, whereas everything above 170 requires top notch performance and a bit of luck. At the highest difficulty level of 250 it is still barely possible to kill a monster, but it should be impossible to beat an arena (except arenas where monsters can fall to their death) at this level. This ensures that the highest score that is mathematically possible is practically unreachable, and that every score can be improved upon.
The controls of the game are displayed on screen if you hit F1 while the game is running, and they are described in the README.txt file that comes with the game. The README file also reveals a cheatcode and describes the parameters that can be used to give Selene tactical instructions.