scratch that, it's been logged! https://github.com/libretro/RetroArch/issues/10688

This post worked for me for the onstart onend runcommands https://retropie.org.uk/forum/topic/11628/240p-and-mame-scaling/12

@Omnija said in [Prototype] Turtle Mini Theme (small screens):

I've uploaded it to the git and added the link to the main post.
If anyone could try it out and give back feedback it would be very much appreciated.

Just tried it out. Looks nice. Just a couple of personal suggestions. The diversity of color you suggested in your previous post would be my choice for each system. Also, in basic view, would prefer game list box to stretch further out to the edges of the screen. Other than that, great job!

@segaages , as @dankcushions said above 480p scanlines overlay:

i believe packaged with retroarch is a Wii scanlines overlay that can be activated. the Wii was 640x480 (or at least, that overlay is) so that should work well. i can't really demonstrate/remember how you load overlays but maybe that's enough to get you going :)

This might be a low-overhead solution for you. There are other threads that have examples of the lines you could include in a retroarch.cfg (either per ROM or per Emulator) to setup an overlay as opposed to the shader. If you can find the file dankcushions is remembering, load it on the Pi and reference it as an overlay, (and assuming you like the look of it) it might be a simple way to achieve the effect without the need to learn OpenGL.