Ok, but what unit? They didnt really rely on spearman.  And Spearman are our only melee unit that doesnt cost metal    And maybe even they should cost metal.  I guess it really comes down to what does the cost represent.  Food to "grow" the soldier, other resources for the equipment used?  Then really most melee have some form of metal armor...  I'm willing to redo our cost system... but I would like more imput and clearity on what it should represent.

Maybe the Ai being harder isn't bad, but I think you should be able to get a cs non ranged unit that doesn't cost metal from cc and barracks. And maybe that is just my bad strategy, but I rely on them alot

Render consumes CPU each frame but without spikes. So if you have freezes then it's simulation if you have lower average FPS then it's render. I plan to reduce the render bottleneck in the future versions by moving it to separate threads.

Do you have V-Sync enabled?

Well p1 there is the spearman, they dont cost metal  P2 yes romes melee unit from barracks is sword and cost metal.... But again I think by the mid repulic they were really standardizing their army.   I do think AI is harder in our game, which is somewhat intended.  I think AI is too easy  Although I'm not sure what level you are playing on.  It might be good to play some MP games, we could play against the AI.