1. There are 6 abilities, including Charisma, Intelligence, Dexterity (the other three aren't from D&D, e.g. Physique or Focus). Their min and max are different than in D&D (I don't know D&D much, though).
2. I have 2 races: Human and Dwarf
3. I have classes like Warrior, Thief, Shaman, Necromancer and a few others.
4. I don't use any trademarked names or creatures with their characteristics (like beholders), but I use common mythology names like "troll" or "giant".
5. I use spell slots. There are two types of spell slots: normal and high-energy slots (so some spells may only be put to high-energy slots).
6. When characters sleep, spells in spell slots are regained.
7. When creatures gain XP (for quests or for killing enemies, etc.), they may level-up. The XP points for a certain class level are totally different from D&D.
8. I don't think there are any other similarities.

A leveling system will be original so long as the formula you're using is custom.

Thanks for you the feedback, everyone. This is exactly what I was (and am) looking for. I know it's not professional legal advice, but I don't need that for the time being.

Ravyne: I think you misunderstood some parts of my post, probably I wasn't clear enough (sorry). So let me clarify it:

• It isn't the ruleset that needed 3 years: it's the game itself. With some friends, we implemented the engine, too.
• I might be paranoid about getting sued (I invested years to this game), but not about others stealing my ruleset. The reasons I didn't want to publish it yet are that it isn't fully finished yet, and I want it to release it together with the game. This is for fans. Anyway, when the game is released, everyone will know the ruleset, so I have no reason to hide it now due to paranoia.

An addition that might be legally relevant: I'm in European Union. I haven't yet registered the company, but it will probably be registered in Germany, The Netherlands, or Austria. The game will be available worldwide, including the US, as well.

An addition that might be legally relevant: I'm in European Union. I haven't yet registered the company, but it will probably be registered in Germany, The Netherlands, or Austria. The game will be available worldwide, including the US, as well.

Be sure to register your brand beyond the territory in which your company is. Patent trolls might otherwise claim the name and mechanics of your game and operate it legally outside of your territory (possibly claiming a lot more marketshare than you).

Just a piece of advice I've recently learned from one lawyer I do business with (her experience with Sega taught me much!)

Thanks for the advice.

Registering the brand takes a lot lot lot money I guess. We're just indie developers...

Anyway the rule system itself isn't so "special" I think; it suits the needs of our game, but it's the game content (quests, spells, stories) that should make our game great.

Or do you mean that they might steal the game as a whole (name, characters, world and city names, etc.), and start to re-distribute it in the same binary form? In this case, I thought that they would almost certainly lose a copyright trial, because it is pure theft (especially because the software itself -- the binary code -- is copyrighted too I suppose.) Or perhaps they would make a new game based on our characters, names, ideas and quests -- I suppose this is the tougher case...

Or do you mean that they might steal the game as a whole (name, characters, world and city names, etc.), and start to re-distribute it in the same binary form? In this case, I thought that they would almost certainly lose a copyright trial, because it is pure theft (especially because the software itself -- the binary code -- is copyrighted too I suppose.) Or perhaps they would make a new game based on our characters, names, ideas and quests -- I suppose this is the tougher case...

Generally speaking, they don't tend to steal your code as is, but they use the same brand/presentation to capitalize on your audience. Of course, this assumes your game gets big first. Perhaps the advice merely holds for when you're beyond 100 000 players and start to garner some serious attention.