Create refraction multiside

Well, I tried to replicate a tutorial I saw in codrops, but by doing it on my own, the expected result does not come out

this is the pen

Any idea why I don’t get this result?

Fixed fiddle:

You have not configured the uniform uReso correctly which represents the resolution of your screen. Without a correct resolution value, you can’t compute proper uv coordinates in the fragment shader.

Apart from that, it seems the current code flips the reflection. Is that the intended effect?