Thanks for the feedback! It all started from wanting to create a game where scaling the UI also modifies the values the UI "contains", so that a visually bigger slider would contain a bigger health pool.
Yes, one of the blue ships is undestroyable via projectiles, BUT it can still be destroyed by boosting into it, which does piercing damage. This is technically explained in the tutorial in the main menu, which is accessible via the arrow next to the game's title . As we believe not many people will notice it I thought I'd mention it here :)