WTF is a "Squircle", you ask? It's a shape that's a hybrid between a square and a circle. It's different than a rectangle with rounded corners because with a squircle, the corners taper off gradually into a flat plane, rather than following a perfect circle at the corners. 

Apple popularized the squircle when they introduced iOS 7 and ditched rounded rectangles for squircles for all app icons.

Squircles give a friendly and playful feel with their lack of hard edges, and the radius of the corners can be played with to get different effects.

The problem with squircles is that you can't easily make one with common settings in a program like Sketch. 

If you'd like to make some squircles of your own,