My title often acts based on timers, and doesn't always have on-screen motion—so I never realized that the Simulator was pausing temporarily every time I poked around on my code in the window beside the Simulator. (I spent hours re-coding my timers in different ways to figure out why sometimes they triggered and sometimes not. Mystery solved!) Luckily I just found the setting for this in the Playdate menu, which defaults to Pause Simulator When Not Active.
Suggestion: make this dormant state more clear—like fading the screen halfway to yellow (or something obvious) to indicate when it's dormant.
Great Simulator app though! The dark mode support and auto-cranking are welcome extras!