A wonderfully polished entry! I had a lot of fun digging ichor and levelling my dwarf abilities (glad I got double jump as my first buy!) The graphics and sounds were perfect and the gameplay was super engaging.
Just one thing I think, please lock the player out from buying "one buy only" items, ie. the jump/drone/pick-axe upgrades. The jump and drone upgrades I did presume was one-only, but the pick-axe I bought again as it seemed to indicate multi-upgrade from the text, however on first buy it was from 6 hits to 3, and the 2nd still still 3 (in case that was not intentional). But I'm nit-picking here, overall fantastic entry!