Thank you for the feedback!
For the shield I used the old school trick of showing and hiding the sprite at ~60hz which gives the fuzzy transparency effect. It's not really necessary with alpha setting available, but it's more authentic.
The initial idea is that you collect the gem which is part of the enemy, like gems from metalheads in Jak II? That's why the center is similar, I wanted to add more particles or animation maybe to give more visual focus for exp but didn't had time.