Collect the gem quota and the exit opens. Walk into it to finish the cave.
Boulders and gems fall when you dig out what holds them up — and roll
off each other. Anything falling on you is fatal. Walking under a
resting boulder is safe… until you stop.
Push a boulder sideways by walking into it for a moment.
Fireflies explode when they touch you. Drop a rock on a
butterfly and it bursts into gems.
Race: everyone digs the same cave; your exit opens at YOUR quota,
first out wins the cave. Crushed miners respawn and spill half their gems.
Co-op: one shared quota, everyone has to get out.