Engineers can rush Walls

Military Engineers can now use their charges to rush building Ancient, Medieval, and Renaissance Walls. They provide 50%, 20%, and 15% of production cost per charge, respectively. Roman Legions can use their charge to rush 50% of Ancient Walls, too. This means that each charge provides roughly the same amount of Production for all Wall types, and a Military Engineer with two charges will cost about twice as much Production as will be provided by those charges (matching the fact that rushing by purchase makes things twice as expensive, too).