grf {
 grfid : "ZUU0";
 name : string(STR_GRF_NAME);
 desc : string(STR_GRF_DESCRIPTION);
 version: 1;
 min_compatible_version: 1;
}

produce (primary_produce,
  0, 0, 0,
  production_rate_1 * (128 + LOAD_PERM(0)) / 256,
  production_rate_2 * (128 + LOAD_PERM(0)) / 256,
);

switch (FEAT_INDUSTRIES, SELF, switch_prod_change, [
  STORE_PERM(extra_callback_info1, 0),
  extra_callback_info1
]) {
  return 0;
}

item (FEAT_INDUSTRIES, item_industry_coal_mine) {
 property {
  substitute: 00; // coal mine
  override: 00;
 }
 graphics {
  random_prod_change: switch_prod_change;
  produce_256_ticks: primary_produce;
 }
}