as someone who has played Johnny Upgrade a lot, this is an idea i appreciate greatly! it's a really cool spin on the theme, and the gameplay feels good. i especially like the JU method of having alternate paths that only become accessible once you upgrade enough. (i went for the same strategy i undertook in JU so long ago; buffing the coin multiplier before anything else, which proved just as effective as it was.)
the single biggest criticism i have is the shooting mechanic. the delay between the input and the shot is very long, which feels unresponsive and clunky, and was very frustrating in the endgame. i also think there was room for more polish in the area of sound effects.
still, those concerns are minor, and overall this is a brilliant product. fantastic work!