rules cannot be trademarked or copyrighted. Putting rules under the trademarked name of Dungeons and Dragons is not the same as trademarking those rules
A trademark is (by definition) a sign. A (representation of a) rule is also a sign (or collection of signs eg E = MC^2). I don't see any reason in principle why the expression of a rule by a sign couldn't be used as a trademark - WotC's d20 logo is getting pretty close to this, for instance.
Well, in the Tetris case they copied the whole game, AFAIK, inasmuch as the end user was concerned.
Knowing nothing more of the case that was has been posted on this thread, what you have said here give me the impression that the publisher of the infringing game was using different code - and thereby trying to avoid copyright infringement - while delivering an identical play experience to the end user. Is that correct? And if so, is the idea of "look and feel" in the case then related to this contrast - which arises in the computing case - between code and end user experience?
I see no bright line between what is a rule, and what is a look and feel, when things like "number of game pieces" and " the way pieces moved in the playing field" is a look and feel and also a rule.
If the Tetris decision is related to peculariaties of computing - and the contrast between code and user experience - then it's not clear to me what, if any, its implications would be for very different modes of gaming in which the end users themselves apply the rules. Hence my question above to S'mon.
Isn't copyright law, in the US at least, predominantly a statutory body of law? I assume that we are talking about judicial interpretation of a copyright statute, rather than common law.
using 3d6 to generate stats STR DEX CON INT WIS CHA very probably would not be infringing.
A precise reproduction of the 1e AD&D saving throw tables would, I think, likely be infringing
<snip>
The general idea of a saving throw table is not protectable though, nor (AFAICT) are any elements derived from a formula, such as "+1 every 3 levels". So the formula-derived 3e saving throw tables might not be protectable whereas the 'messy' 1e tables probably would be.
Your ability scores are both rules and look/feel. Hit points are both rules and look/feel. Armor Class is both rules and look/feel. Alignment is both rules and look/feel. Move rate is both rules and look/feel. There is no realistic distinguishing line between being a rule and also being look/feel.
For what it's worth, my intuition is that armour class, hit points and movement rate as numerical representations of hardness, toughness and distance per unit of time would be like the non-copyrightable examples that S'mon gives. But that having AC 9 or AC 10 = unarmoured, and AC 3 = plate mail, etc, might be closer to the example of "number of game pieces" and hence copyrightable.
My feeling is that the description of a human being as characterised by six stats STR INT WIS DEX CON CHA might be in a similar category.
And the D&D alignment system strikes me as not just "look and feel" but itself a substantive story element from which similar game elements in other games could be fairly said to have been derived. (The idea of alignment wouldn't be like this, but I would have thought you would have to use different alignments.)
S'mon, any thoughts on how far off target I am in the above?