I was in full screen but I still couldn't see the upgrades. Also, the riflemen are too powerful to the point that the game becomes too trivialised.
Thanks for sticking with it – in 0.1.10 the shop sits in a column next to the field, so you can see defenders and upgrades without scrolling or full screen: The Last Line 0.1.10: see the shop, speed it up. On the riflemen being too strong: noted, I'm checking how armies are built at later threat levels before touching the balance.