There's no need to be rude. Insults like this don't add to your argument.
> 1. It does only save one solution for each level but if you can do it in fewer nands, why do you need to keep the fewest components? Most puzzle games like this work this way
Because they're separate optimization goals. I want to hit all of them and have each of them saved. Compare Zachtronics games, as magnostherobot mentions. Also, the ones with fewest components will typically be conceptually clearer.
> 2. In later levels it uses your best solution from previous levels. The basic (non-optimal) xor solution has 3 compents with 6 nand. The first time I did half-adder, it told me my solution was 2 components/8 nand (a 2-nand AND plus a 6-nand XOR). After trying for optimal xor again (and failing), solving half-adder shows "2 components used. Mission XOR is not completed, so the total number of gates could not be counted." So it uses YOUR best solutions.
Thanks for determining this. But it would be better if, you know, the game said this anywhere. None of this is explained.
> 3. I mean it's pretty obvious. optimal == fewest nand, simplest == fewest components. If you optimize for nands, your solution is going to be less simple/more complicated.
I have to disagree that this is "obvious". I'm sure one could figure it out after playing enough, but one shouldn't have to; the messages could easily be made more explicit. And like note that even this isn't exactly a correct description, because if you come up with a solution that minimizes both, it only says "This is optimal!" rather than saying "This is simplest and optimal!". You see the problem?
And honestly I'm just not sure you're correct. Like doing NOR the obvious way, I got a "this is simplest!" message, but did not get a message saying to do it in fewer NAND gates. So what does that mean? Is it optimal or not? If yes it ought to have told me; if no it ought to have given me the message saying it can be done in fewer.
So yes I do think the game is really being badly unclear about this.
