masking sprites

im making a whack-a-mole clone:

https://www.youtube.com/watch?v=gTXuOCnZc3Y

i have a simple picture as the mole, attached to a prefab. How can i mask the mole as he goes back into his hole? ive found some stuff using shaders but tbh that is way beyond me at present.

What i am using now is having the background below the mole hole on a different layer so that you cant see the moles body moving, just his head coming out.

What better ways are there of doing it?

How can i mask a sprite in a certain area?

 

That's what I'd recommend.