1) It had to give the players freedom to create their own adventuresThe first - freedom of action - is common to all table-top roleplaying games and is one of the things that makes them so enthralling. ZOMBIEPOCALYPSE was created in direct reaction to the cliche reactions of the heroes of slasher flicks, who always seemed to do the same thing: run around in dark forests until the monster picked them off one by one. My friends and I began playing it as a "what if" experiment to let us see what we would do were were placed in a similar situation, but our adventures quickly grew beyond the stock circumstances common to the movies. We fought zombies on the farm, in the city, in the mall, on the sea, in the desert, and even in space. We ran from them, we built forts to stand up to them, we tried to harvest and tame them, we even tried talking to them.
2) The system had to be simple and fast
3) It had to be easy to learn
Unlike almost any other game, role-playing games give players the opportunity to do almost anything that comes into their minds; they aren't stuck with the limited options thought up by the guy who wrote the game (me!) or the person running it (the game-master). Faced with a horde of zombies, players might run, or fight, or hide, or any of a million other things. This ability to self-determine the direction of your own story was something we very much wanted to maintain in our games and - when compared to all the other zombie-related merchandise on the market (movies, comics, video games) - is one of ZOMBIEPOCALYPSE's great strengths.
The second tenent of ZOMBIEPOCALYPSE was an overriding urge towards simplifying the rules system. ZOMBIEPOCALYPSE started as adventures for the Dungeons and Dragons (tm) game, but as the years rolled by, we increasingly pared back the rules until its origins were barely recognizable. Our ZOMBIEPOCALYPSE adventures were always short, fast and brutal; they were one-off stories where both the GM and the players were freed from the loftier considerations of our normal D&D campaigns. They were a chance to let our hair down, as it were, and the changes we made to the rules reflected this. For instance, when it became obvious that our characters were going to die - and die a lot! - we revamped the character generation system so you could get a new PC up-and-running in minutes. Combat was pared down to a minimum of dice rolls. We dumped experience points, levels and even hit-points. Everything about the system was geared towards getting the players into the action in a minimum of time and then keeping that action going throughout the session with little time wasted looking things up in rulebooks.
Actually developing a system that simple is surprisingly difficult and writing ZOMBIEPOCALYPSE is a constant balance of providing enough rules for the myriad of actions the players might take without overburdening the GM. It would be so much easier just to throw in rule after rule for every possible interaction I could think of (e.g., Rules For Smelling Zombies) but this would just add unnecessary bulk to the game and slow things down not only to the point where the game is no longer fun to play, but actually impractical. Keeping things simple is in fact the major challenge facing the development of the ZOMBIEPOCALYPSE and one I continue to struggle with. Whether I will ever achieve this elusive balance is still uncertain but I will continue to strive in that direction.
As important as simplicity is, I also wanted the rules to be easy to learn for newcomers. Many modern role-playing games - some of which have been developing for over four decades - have become incredibly arcane, with rules encompassing multiple (and hefty) tomes. They can be incredibly intimidating to newcomers to the genre.
ZOMBIEPOCALYPSE is being purposely written to counter that. Its rules are simple and short. It uses a familiar setting. It does not use any of those strangely-shaped dice that other games use, just a regular cubical die with six side as might be found in any household. There are a minimum of rules and tables, there are no classes, no arcane powers or algebraic equations necessary to determine success or failure. In fact at heart there's only one basic rule that needs to be memorized: call an action, roll a die and if it's a 4, 5 or 6, something good probably happens and if it's a 1, 2 or 3, it's probably bad.* And judging by how quickly I've seen newcomers pick up the game, it's a worthwhile and appreciated goal.
As I continue to develop the game, I always keep these three tenets in mind. I always question whether the changes and additions I am making are going to interfere with the player's freedom of choice, or if the rules are even necessary. Its what drives me to add, change or delete rules. Hopefully all the effort will result in a product that is both interesting and fun to play. We'll see!
* Okay, it's a bit more complicated than that but that's the core concept to pretty much every rule in the game