Using a mask shader for creating pop/explosion effect?

I would love to get some help on constructing a shader that can achieve these effects:
Examples: Super Time Force explosions and Mt. Mograph Accent Explosions

I was thinking that you could do it by scaling a square or circle shaped mask up.
I have little experience in programming shaders, so help is absolutely appreciated.

Note: It’s for a 2D game, which of course is sprite based. So the shader should be able to be applied on sprites.

Thanks a ton.

You could use gradient masks as animation data in a custom shader. Although I don’t know the code off the top of my head, here is a video by Making Stuff with Unity that may help point you in the right direction. Check out their channel if you’re interested in learning more about custom shaders.