Thanks for playing!
This is our first time really trying WebGL so we overlooked a few things like that, but at least we know for next time!
The general idea was meant to be killing the enemies made protecting the crystal easier, but at the risk of putting you closer to death but admittedly we didn't get the balance quite right, also you only get your shield back if an enemy dies.
If we were to develop it further we'd probably want different enemy types to encourage you to take our some enemies but leave the weaker ones around of something.