Thanks to new code added to the game, I am able to complete my blacksmith tech trees with "Forging" and "Metallurgy" techs.    Forging Reduce the cost of Blacksmith techs by -25% and unlock all other blacksmith techs. Research time: 40s   Metallurgy Reduce the research time of Blacksmith techs by -50% and unlock all other blacksmith techs. Research time: 20s   So, neither cost resources, but you must choose one or the other in order to star