This is cool! However, is there a way to control an operation using more than 1 input?

Like, can I say negate index 1 insofar as both index 2 and index 3 are on?

I tried adding two identity things and an x thing, and selecting the 3 of them, but the "c" button wasn't enabled when I did that.

Uh, that is still unitary, right?

Ok, yeah, it still permutes the 8 pure states, and permutation matrices are orthogonal, and therefore unitary, matrices.

edit: Oh, I see, in the https://quantumjavascript.app/Q-Gate.html page it says that that gate (apparently called the "toffoli gate" or the CCNOT gate) is "coming soon".

So, it will be added, but hasn't been quite yet.