Well done! Very polished look and feel. Gameplay is fun.
It's definitely a bit tedious to get the upgrades, as the beginning is very easy but you get quickly overwhelmed when the stronger enemies appear (lvl 2 black ones and lvl 2 skellies). Also, a pause button would erally help since progress is reset when restarting game. But overall, great game, definitely one I've played for quite a bit.
Great job!