I liked this =] I wasn't good at it, until I was, and that's when I knew it was working.
Various thoughts copied and rephrased from thinky puzzle discord:
"[regarding the situations where the solution doesn't require using all cards] I love when a puzzle game has chekov's guns that it never fires red herrings. Or to put it another way, I love when puzzle games are naturalistic, when the fingerprints of a designer are fully absent, our attention is focused entirely on the puzzle itself (though I acknowledge that conveying the thoughts of the designer is a core part of most puzzle games)
"I guess it's that... frontier problemsolving irl is mostly about looking for ways of breaking all prior theorists' assumptions, so if games never cultivate a delight for breaking the designer's assumptions and only reward staying inside of the frame, that's trouble.