Alternative screen saver idea
Much as I like your turtle slowly swimming across the screen. It does have the one disadvantage of not being able to see the volume at a glance. One alternative screen saver would be for the volume and input name to move around the screen. Maybe full animation of every minute move the position a little. I understand OLED displays can suffer from a type of ‘burn in’ so appreciate the need for moving things around. Just a thought. Maybe a setup alternative setting?
I will give that idea some thought. Perhaps add a screensaver menu option to select either "swimming turtle" or "shifting/drifting volume". In an early OLED display prototype we left an image on 24x7 for several weeks and it did indeed "burn-in" the image. It wasn't terrible but after a few years of being on all the time with no changes it would probably be quite noticeable. Hence the screensaver concept at all.
Maybe a slow pixel shift to the right. Drop the volume bar. So we know it’s in screen saver. When up to the right boundary. Drop down to bottom boundary and then slowly shift to the left boundary, then up and so on, a slow clockwise movement. Keeping the input name and numeric volume enact all the time. Less jarring than blitting randomly on the screen. Key for me, would be to ensure complete display. Avoiding cut off at the edges. Slow rotating or random blitting In this way would be great.