This is a fun game! I really liked the goblin idea, nice use of the assets.
I'd just try to make the power selection less subtle. Does the power increase exponentially the longer you maintain pressed the mouse? Maybe it would feel better if the growth were more linear, not so exponential, that'd give users more control on the hit.
I'd focus the difficulty of the game not so much on the user input but also on what's the correct stick to hit the goblin head, the right power, angle, etc. On my case if the main difficulty is on trying to hit one pixel more one pixel less is a little frustrating.
But overall it was a fun game, congrats!