Stable clock. I think I read somewhere that it's not worth the effort but I disagree :). I would love for the drum machines and sequencers to play on time. What if it was written in C instead of Lua? I think the app has great potential.
The problem is the Playdate is single-threaded, so any slow down on the one and only thread affects everything, including the timers/clocks. I am thinking about adding external midi clock sync which would make the timing precise, but it would require a little technical know-how from the end-user (it would use a small Processing.org project as an intermediary bus between the host system, and the Playdate: https://github.com/orllewin/playdate_midi_bus - you can already use an external keyboard with that, but if I can find the time will add midi clock too)
the play date audio device maintains its own time separate from the standard clock … I wonder if this is affected by frame rate slowdowns?
https://sdk.play.date/2.2.0/Inside%20Playdate.html#C-sound.time