I know this is a small thing, but I often forget to quit pico-8 and I leave it running in the background overnight, which prevents my Mac from sleeping. Maybe it could be tweaked so that pico-8 only blocks the display from turning off/computer from sleeping when it's in run mode?

I tracked it down to pico-8 by running pmset -g assertions which showed:

   pid 164(coreaudiod): [0x001a40d7000197e9] 11:05:27 PreventUserIdleSystemSleep named:
 "com.apple.audio.AppleHDAEngineOutput:1B,0,1,1:0.context.preventuseridlesleep"
    Created for PID: 93582.

PID 93582 is pico-8. So it appears it's because it's keeping the audio channel open.

+1. It would be great to fix this. Both sleep and my screensaver don't seem to work properly while PICO-8 is open in the background.

+1