Can you set a collider inside out?

Hi everyone,
I have a student who has a game he is designing with a duck sprite, inside a bubble sprite he created.

He wants to make it so if the duck hit the bubble wall, the bubble pops and the game is over.

The problem is that colliders typically border a sprite and go around the outside. He has a bubble he made, and wants the collider to go on the INSIDE border of the bubble - essentially turning the collider inside out. Is this possible?

here is the start of his code:

thank you!

That could be a little tricky. Honestly, I’m not sure it can be done that way since even “empty” pixels are part of the sprite, so the duck being inside the bubble is constantly in collision. You may have to create a group of sprites that when together surround the duck, but move synchronously with each other.

Maybe someone else will chime in with a possible solution?