I feel like at least for me it's kind of hard to tell what happened when I try to attack. Maybe I'm just not used to the genre, so I have to make an effort to look at the health and the place at the bottom that says what happened (which doesn't seem to automatically scroll down so I have to scroll it myself), but also I notice there isn't really an animation or sound effect for getting hit, just for attacking. (I think Pokémon has a different sound effect when you do a super effective attack, so something like that might be helpful.)
Are Weak Skeletons supposed to be groups of enemies? When I've encountered them it says the enemy is killed and then the skeleton's health goes back up again. I thought at first maybe the game had glitched and I was stuck.
My first attempt failed when I encountered a Soldier Skeleton with -4 health and then the game showed an error when I tried to attack, and later I somehow encountered a Demon Lord near where you spawn after running out of health, which also caused an error.