I don't know how I feel about the message "This is optimal!" displaying when you use one NAND gate to build an inverter at level 2. Level 1 forces you to build an NAND gate out of (1) an AND gate, plus (2) an inverter. It feels like it'd be more optimal to just reuse that inverter.
(And then level 3 is an AND gate, the other primitive† you started with...)
† Technically, you start with two primitives, implementing f(a, b) = a ∧ b and g(a,b) = ¬(b ⟶ a). You also get the ability to provide 0 and 1 as fixed inputs, thus ¬a ≡ g(a,1). What you lose after implementing the NAND gate is the ability to provide a fixed 1 input - instead, you are informed that you assume all gates automatically draw from this. Worst of all possible worlds.
