Thanks for the feedback, much appreciated!
I wanted stamina to be scarce :) You get also HP back when killing an enemy, I was thinking about a mechanic to force the player to push forward without waiting for the stamina and HP to refresh, but haven't had any good ideas.
Spoiler: Having stamina full, red and blue enemies can be killed pretty easy by using the shield on the first enemy attack timed so there is enough stamina left for 3 hits. That's a pretty save method to kill reds instant and blues only needing one more hit.
And sorry for the audio, I know that's an even weaker area than my pixel skills :(