I am not a game expert, but I found an excellent article in
http://research.cs.queensu.ca/~dalamb/Games/design/design.html#Ques2.2that says the following:
2.2 How can I protect my ideas?
Well, I've got good news for you, and bad news. First the good:
If you're in the US, England, any Western European Country, Canada, or Australia, anything you write is automatically considered to be copyrighted under the terms of the Berne convention that all these countries adhere to.
Now, the bad news: a copyright does not protect your ideas. All a copyright does is protect the _expression_ of an idea. Thus, it's perfectly legal for someone to take all the rules of, say, Advanced Dungeons & Dragons, paraphrase them, and eliminate references to Dungeon Master and a few other terms TSR has trademarked, and sell the resulting product.
That said, including a copyright notice in your work does give you one benefit: it makes it easier to collect damages if someone does copy your material. If there is no copyright notice, the copier can claim "innocent infringement" (that is, "I didn't know I couldn't copy it") and get off with a slap on the wrist. In addition, you may want to look into registering your copyright. In the US, at least, this provides definite proof that you wrote your material first, and allows you to collect money from copiers beyond simple damages.
To protect the ideas of a game, a patent would be necessary. In general, though, it's probably not worth the effort. To qualify for a patent, a game must include physical components beyond simple board, dice, and rules, so that it can qualify as a "machine." Thus, most games won't be eligible. In addition, obtaining a patent is a long and complicated process which will almost certainly require you to hire a patent attorney, pay his/her large fees, and pay a large (and nonrefundable!) amount of money for a patent application.
In my opinion, though, you needn't worry about protecting your ideas. Chances are that if you've thought of it, someone else has as well. Thus, refusing to discuss aspects of your game in order to protect your ideas isn't likely to keep anyone else from using that idea, and will prevent you from getting feedback which might help you improve the idea.
(A bit from my own experience: a few years ago, I came up with an idea for a die-rolling method for an RPG which I had never seen before and which greatly simplified the system I was making. Since then, I've encountered at least three systems which also use the same method, none of whose authors could possibly have seen my work.)
In general, games do not succeed because of any single "neat idea;" in fact, innovative games are less likely to succeed because most people do not want to learn large amounts of unfamiliar material.
For more information, try these web sites:
* Ten Big Myths About Copyright Explained
* The Copyright Website
Good luck!
Lisa Lloyd
www.LloydMarketingGroup.com