How are you supposed to flag all the mines when the field keeps changing? Maybe make it so any flagged mine stays a mine and possibly any cleared space stays cleared. I think the last one would probably make it too boring, but having mines stay could probably work.
Basically you should wait, until all the reactions stop and transform into either stable shapes or oscillators, which you can predict. I made this game just as an experiment and I want to keep it very customizable, so maybe I will add "pinned mines" as an option. Thanks for feedback! I wonder if this project will grow into some competitive field.