Hi Tassadar. The system you’re describing is not totally new. In at least the broad outlines, it is similar to Savoir-Faire, by Emily Short. Savoir-Faire also has a magic system whereby items can be linked, but there are limitations and logical congruencies that need to be taken into account in order to link things, and to deal with them once they are linked. If you haven’t played it yet, you definitely should, not only because of the magic system, but because it’s a really good game
Re your example: I would like to see you look a bit harder at the way you implement the linking, and specifically narrowing somehow the ways in which objects can take on one anothers’ properties. Opinions may vary on this subject, but it seems as though there’s a lot of potential here for behavior that looks arbitrary to the player. My feeling is that this is probably not a good thing, though one might argue that it also provides comedy and/or an element of surprise (and, hopefully, delight). YMMV. But here’s how I responded to the example, which may help explain what I mean.
First, I don’t understand why we would want to link the parrot to the card. Presumably if a card-parrot can fly and carry out commands, the parrot-parrot could do this to. So why would I bother linking the two? Wouldn’t it make more sense to order the parrot to grab the card and carry it up to the shelf?
More importantly: you mention that the parrot will become thin like the card when the two are linked. That’s a perfectly understandable physical manifestation of the linkage. Yet there doesn’t seem to be any physical explanation for the new abilities of the card. That is, without wings, the card can’t fly like the parrot; without a brain, it can’t cogitate like the parrot; without ears, it can’t hear like the parrot. How is the player to predict what will happen when objects are linked? Also, how would communicate the new abilities of the card to the player? Unless the card actually turns into a thin parrot, how is the player going to know that it can now fly (or, even more extreme, understand commands)? And if the card becomes a thin parrot, the question is the same as the one I raised in the previous paragraph: why do we need to link the parrot and the card at all?
(In the same line: If any two objects can be linked, why bother with the card at all? Couldn’t I just order the parrot to sit on the shelf and then link it to the bowling ball?)
The card (or the parrot) taking on the weight property of the bowling ball is a bit easier to get. But, in terms of my critique of the card-parrot link, is it also possible that the card can now “roll” like a bowling ball? Knock down things much bigger than itself? Physically, of course not. But if we apply the same non-physical transformations that apply in the parrot-card linkage, then yes…
To sum up: This is a cool idea with a lot of potential, but I think that your example would benefit from a bit more attention to the mechanics of the system, and your game (and the difficulty of implementing it!) will probably also be improved by placing limitations on the ability, as well as making it more “readable” to the player. What kinds of things can be linked together? Can anything be linked to anything else without bounds? Can only portable objects be linked? Does the player need to be able to touch both objects to link them, or only to see them? (Could linking be done through a mirror?) How will the player know what properties will transfer in advance of linking them? And so on…
Hope this helps!