So you don't need to actually do anything to gain levels... Just have a production building at level 2 and keep firing then hiring the same worker and it turns 1 energy to 1 exp everytime. Might not update but a quick refresh to the browser will clear it up. Works well If you have excess energy and dont have enough workers/resources to do anything productive
huh?
If you have extra energy that is just gunna disappear from not being used turn it into free experience by doing what I said... Also - doesn't need to even be level 2 building can use pretty much any building