EDIT: he beat me to the comment haha
Thanks for playing! appreciate the detailed feedback!
My partner did implement a randomized pitch for the digging sound but it did seem to be pretty hard to tell the change with the sound effect itself, we could probably increase the pitch change to try and make it easier to hear.
we had also implemented a sound effect with the combo it would go through the A minor musical scale which is where the play on words for the name came from. We ended up taking it out as it also seemed pretty annoying with the music and other sounds and long combos, but something we would like to re work in the future! we have the visual counter in the bottom corner for combo but I think it would be nice to maybe have an X combo indicator tied to the cursor to make it easier to see.
and bigger upgrade buttons hopefully soon to come! I too had the same problem with trying to click it sometimes while doing some play testing, but I didn't get it changed due to time constraints