Nice game! I liked the enemy variety, sprite work, the journal entries, and not to mention the turtle cameo for the wildcard.
A couple points of feedback/suggestion:
- I wasn't sure how to use the serum syringe (found out by trial and error it was F), so worth listing in the controls
- Would be nice to have some indication of when you're taking damage
- Could be good to have a charge up animation for the mutant boss' laser so you have time to find cover
Overall nicely done!