Your browser does not support the Houdini CSS Paint API yet! View supported browsers 
--smooth-corners: 4
mask-image: paint(smooth-corners);
-webkit-mask-image: paint(smooth-corners);

Update: add a smooth corner painter that better supports rectangle.

Original

V2

V2 5 R1
V2 4
V2 5
16, 2
5
4
2.6
2
0.6, 2
1.2
1
0.8
0.6
6
8
10
12
14
16
32
64
80
96