So that skeletons do not scare you, do not go ahead of them. Just stand still and fight back from them. And with the bosses, on the contrary, do not stand still. And do not use crystals for nothing, they are needed to defeat the bosses. Using the power of the crystal against bosses you increase the chances of winning.

https://ldjam.com/events/ludum-dare/45/bna-crystal-power