Entertainmanet Center is located on the Cultural branch of the tech tree, not the Entertainment branch. (Retribution)
If, as a player, I go down the Entertainment branch, I get to unlock all these cool fancy approval buildings that I CAN NOT use untill I open up the Cultural branch, because thats where the first approval building is located....grr.
To top this off, the first Cultural building (Consulate) is in the Government branch of the tech tree....more grrr. I know the name kinda makes sense it is located where it is......but its a CULTURAL building and should be in the Culture branch instead of you know the Entertainmanet Center which has naff all to do with culture. GRRR.
Incosistancies like these plague this game. Grrrrrrrrrrrr.
Rebalance your Improvement costs too, you have moved them all aroudn on the tech tree, pushed most further down the line and well, costs remained the same, for example Space Elevator is now 3 tiers into the engineering Tree yet its costs is still 25. Again more inconsistancies.