This is a spinoff of sorts from 4th edition D&D. The basic premise of Gammaworld is summed up as "Every parallel universes kitchen sink filled with every other universes stuff".
Imagine that the Large Haldron Collider was activated and instead of forming a black hole, the earth was suddenly merged with an infinite number of other earths. each of these earths are parallel universe versions of your own, so basically anything that you can imagine is possible, because in an infinite universe, all things are possible.
The physical world has been damaged by this. The landscape is a mixture of futureistic cities and primitive establishments. Have a drink with an elf at the local ale house, then go next door to the empire state building, climb to the top and view mount doom from a set of binoculars made for beings with 8 eyes.
The peoples of this world are also affected...mutants, fantasy based creatures, monsters. little of this has full consistancy of any one world or peoples.
Character creation is Gammaworlds most obvious variation of dungeons and dragons. Its almost completely random.
Your first decision when playing gamma world is based on 2d20 die rolls.
Die rolls on the core rules of 6 and 16 (see below) would yield Felanoid (Cat person) and rat swarm. However very few things are taken literally in Gammaworld. The fun and humor comes from your imagination of how this is presented.
Lets say for instance that I've chosen to be a swarm of sentient cats based on these two rolls.
I could also be a pride of lions, or a Cat person that has tamed a swarm of rats that constantly crawl over its body to form a shield.
Core set :
8. Gravity Controller
11. Mind Breaker
12. Mind Coercer
16. Rat Swarm
And from the upcoming boxset.
(taken from Mostlyjoes post).
Weapons and armor are simplified. you basically have your choice of light weapon or heavy weapon, light armor and heavy armor. What form these weapons and armor take is up to you. The damage is the same for each type and the armor bonuses you gain are the same for each type. You want your armor to be boba fetts armor? go ahead. You want to wield as your weapon a giant shark? go ahead. One of our test group decided to wield han solo in carbonite as his weapon. (I didnt have the heart to tell him it really was just part of that coffee table replica and not the real thing).
Healing is much rarer. While you have the equivilent of some consistant 'at wills' and 'encounter powers' based on your roll choices you also get passive or dynamic abilites based on cards you draw at random. these decks can be customized for your character based on there various base type. (For instance the rat or the yeti is a biological, but there are other types as well).
Just remember, if you just play this straight then your probably going to be bored. You and the group you play with need to contribute imagination and roleplaying to really bring your strange characters to life.
Example of my first game:
A friend of mine is an official DM and gets alot of preview copies of rulebooks and games, and last night he brought over the gammaworld starter set. We played a game with some friends and i just wanted to share some impressions to anyone looking forward to this.
First and foremost, this game has one massive difference from D&D...the character creation. We all had alot of fun making our characters and giving ourselves backstories, picking out weapons and armor that suited our imaginations, but honestly once the game actually started theres not a ton of things that differentiate it from standard D&D except the theme and the cards.
I randomly rolled my character...my primary class was a yeti. My secondary was giant. So i was a giant yeti. My random bonus skill...oddly...was science. I was rocking a 5 int, so I decided my giant yeti was going to tool around in a multi-pocketed labcoat stuffed with copies of national geographics and encylopedias as his heavy armor. He also wore a monicle. My character (Naturally) as a young giant yeti discovered a book "By a 'Charles Darwin' that suggested the existance of a creature that was inbetween apes and humans. I vowed to one day to use my science skill to disprove this theory. My name is Link. Oh, and my gear was pretty awesome. I had a canoe, diving goggles, a laptop, a radio celphone, and a butane lighter. I also was wielding a lawnmower. (two handed)
My fellow players were 1) A giant rat swarm 2) a TK mentalist 3) A radioactive speedster 4) uhm...Some kind of golem robot i think.
Me and the rat swam had some issues. For some reason he didnt like it when i picked up one and ate it, but we persisted.
We played through a sample game and had a fight encounter. This was pretty standard D&D rules, the cards we had drawn were essentially encounter powers, some were usable once, like a burst effect that keeps people from attacking you, others were persistant effects like a resistance to physical damage (10) or so. Each of the cards gives you the option to overpower it so to speak...you make a saving throw, under 10 and the overpower fails, which is usually a negative effect, over 10 and its super effective. For instance, I had a card that let me grow wings and fly x spaces for one turn...if i overpowered it successfully, I got to keep the wings for another turn after use, if i failed then i would fly in a random direction and crash taking a good bit of damage in the process. We werent hesitant to use the alpha encounter cards because they would have been replaced at the end of the encounter anyway.
Each of your primary and secondary class traits has an at-will or encounter power that is permanent to your character.
I think this game is going to appeal most to a group of people that work to make the game funny and interesting through imaginative play. a few members of our group fall into the category of 'near-gamers' where they play and enjoy it as a gaming experience but the really dont get into the roleplay at all and those people didnt seem to enjoy it as much. My scientist yeti was constantly making very uneducated comments at every turn, and whenever he would attack he would attack FOR SCIENCE.
The card mechanism is interesting in that it gives you the option to use a different encounter power then one you would be locked into such as a D&D class would. I think it could be easily adapted for D&D to have a random set of encounter powers like this however I dont think gammaworld in this area is so worried about balancing the powers as much as they are making them fun and interesting so it may not fully work in a strict rule system like D&D.
I think if I were to find fault with gammaworld is that even with the cards making things a bit more interesting the gameplay just has not really been changed enough when it comes to combat. This might not be a problem for most D&D players, but I do admit that i expected more differences then i experienced.