Chainsaw things

Hello, I've made this simple game and want this trunk to be actually cut. Can you give me any ideas how to achieve this effect? Tree and Chainsaw are both 2D sprites.

 

there are plugins for slicing sprites,
https://www.assetstore.unity3d.com/en/#!/content/12911?stay=yesofcourse

have seen some free sprite fracture/slice scripts too.

 

Do you have any idea on how do I check "progress" of cutting trunk? I want to see the bar on the left which shows how much of trunk have I sliced. For example if chainsaw goes halfway it shows 50%.

 

Ok, this idea is probably not perfect, but it's just ok for now. I will check how many of colliders on trunk collide with collider on a chainsaw.