code: function goDown(arrStartUnits){
  		conn.query(
  			"SELECT unit, level, latest_included_mc_index, main_chain_index, is_on_main_chain \n\
  			FROM parenthoods JOIN units ON child_unit=unit \n\
  			WHERE parent_unit IN(?) AND latest_included_mc_index<? AND level<=?",
  			[arrStartUnits, objEarlierUnitProps.main_chain_index, max_later_level],
  			function(rows){
  				var arrNewStartUnits = [];
  				for (var i=0; i<rows.length; i++){
  					var objUnitProps = rows[i];
  					//if (objUnitProps.latest_included_mc_index >= objEarlierUnitProps.main_chain_index)
  					//    continue;
  					//if (objUnitProps.level > max_later_level)
  					//    continue;
  					arrNewStartUnits.push(objUnitProps.unit);
  					if (objUnitProps.main_chain_index !== null && objUnitProps.main_chain_index <= max_later_limci) // exclude free balls!
  						arrLandedUnits.push(objUnitProps.unit);
  					else
  						arrUnlandedUnits.push(objUnitProps.unit);
  				}
  				(arrNewStartUnits.length > 0) ? goDown(arrNewStartUnits) : handleUnits(arrLandedUnits, arrUnlandedUnits);
  			}
  		);
  	}
docs: direct shoots to later units, without touching the MC