The nand-count is based on how you built the components involved. So optimizing a component will have have cascading effects.
"This is the simplest solution!" means the solution with fewest individual components on the canvas. I realize the text could be clearer.
1. The blue on purple color scheme is a little hard on the eyes. Changing the blue lines and circles to #0f0 green helped a lot. (Green also has strong "on" semantics)
2. My SO and I both had trouble finding the trash can. We both tried to drag components back to the workbench or off of the mat to delete them. A larger trash can icon or just making it red might help.
3. I ran into some z-layering issues (at least on Firefox). Opening a component info bubble from the workbench displays under the mat. Also the "results" popup displays underneath any components that might be on the far side.
Overall great game though! I had a lot of fun with it. Thank you!
Yeah if you see my comment below I think really it should always be explicit both about whether you used the fewest components and (separately) about whether you used the fewest NAND gates. Currently it seems like you sometimes only get told about one or the other...