Defense question

[oagersnap]

This is probably a really stupid question, but how can I buy anything in Defense? When I start the game, I am in the "build phase", but the only things available is the city tool, which does nothing, and the button that takes you to the tech tree, and all the techs there say "Cost: 0 gold".

I'm sure the answer is really obvious, but I just got the game and I can't figure it out.

 

[ese-aSH]

indeed it is obvious... everything is in the pop up where you can buy cities or units.

(hard to describe since I never pay attention to it )