That's a good idea to add a visual (and auditorial too) indicator to collecting a checkpoint! A fun fact is that the checkpoints were ONLY indicated by a small point-light with no particles until pretty much right before submission, but I added particles since someone in the server said the lights weren't a very clear checkpoint indicator.
About the bug where you have to close and re-enter full screen, was this happening with the Web, Windows or Linux build? When running the Windows version with Wine on my linux system, the audio gets glitchy after transitions, but it works perfectly on actual Windows computers.