God I am so happy people remember and appreaciate that game, makes me less pasimisitic about the future of Frontier.
There's definitly a way to upgrade! Press U while hovering over the building. You can watch\read the tutorial for more info (in game tutorial is simply too "expensive" for a 60 hrs demo)
A quick tip. The upgraded turrets are stronger and have a longer range, but they don't cope that well vs. the fast enemies.
I'll check that scrolling bug.
Thanks for the feedback!