Newpixie missing shadow mask

[mtmrc]

Looking at the shader code from RetroArch is seems you replaced gl_FragCoord with just uv_tx instead of uv_tx*ScreenSize.

Also ghosting effect seems much stronger, but I personally comment it out so I didn't look into it.

[vanfanel]

I can confirm what @mtmrc said.
I did a PR that will fix this: #19