Config :
"luck" : luck sets the probability for an event to run. Higher the luck is, lower an event has a chance to run.
"radius" : radius define the max radius where something can spawn (ex: tnt, sand, lava).
Sandrain :
harder : the probabilities for a sand or a gravel to summon are increased.
hardcore : summon sand and gravel directly above players.
playertarget : increase the probabilities for a sand to spawn closer to the player.