Bit of a random question: how does one find out which Lego patents are expired?

A patent is a deal made between you and the government.  They're protect your product from being copied for a set amount of time, but you have to tell EVERYONE exactly how it works and when that time period is up anyone can use it for themselves.

Want to know why so many things use Velcro?  Patent expired.  Now anyone can use it.

That's the deal.  You can try to keep how your shit works secret in perpetuity, but if you do the government does not have you back if someone else makes things using your ideas.  Why?  Innovation only works if ideas are shared and anyone can build on them but people are less likely to innovate if they won't reap some of the rewards, so the patent system is a trade off.  The government will enforce your monopoly on your invention for a time, but in return you have to let everyone play with it when that time is up.

Some Lego patents are really, really dead.  Dead, buried, decomposed, and recycled as firelighters.

So you have other brands making completely legal knock offs.  One brand, called Mega Bloks, is friends with various companies and thus able to make Lego-compatible Barbie, Skylanders, Sponge Bob, Halo, and Assassins' Creed figures.  Hasbro has its own lego clone line, because why would anyone want to be without Lego-compatible transformers?

Some companies just make bricks, for building, because it's getting harder and harder to find a decently priced box of bricks from Lego.

But, the thing is, it's unclear to me exactly which Lego stuff is up for grabs and which isn't.

The basic Lego brick itself, the studs, the dimensions, so forth, these things are all very much up for grabs.  The original mini-figures, I know, are also fair game.

But the thing is, Lego never stopped making new shit.  Friends "mini-dolls" (why can't you just call them, "mini-figures" ones that finally look vaguely like people) are a recent invention and thus it would be incredibly surprising if they weren't patent protected.  (And a massive fuck up on Lego's part.)

But where's the cut off?  I cannot seem to find a list on which Lego patents are expired and which are still in force.  Hell, just finding a list of all Lego patents is hard as hell.