really awesome potential!
just a little bit of tweaking, and you've got a gem here.
Here are some suggestions, but please feel free to PM me for more in-depth discussion:
-brighten up the colour scheme. The energy bar is light grey on white, and frankly, it's not easy on the eyes. The upgrade menu could also be brightened up a bit.
-slower energy drain, less damage from impacts. the square's occasional irratic movements make collision avoidance impossible at times, and then whenever I feel like i'm doing well, I suddenly die due to energy loss. Boost the amount of energy you receive from the red squares as well. Some seemed to give me a lot while others did almost nothing for me.
-upgrades are all good, although you might want to arrange them by type and cost. Yeah, that would help. Their current ordering does look a little random.
But yeah, I played it a bunch of times only to be thwarted when I start to feel like i'm getting the hang of it. I think that your primary concern right now is getting the energy properly balanced, then you can make it look nice and sound cool.
I will definitely be keeping an eye out for the second version. After this is polished, I feel that it's going to be a VERY popular and fun game. Again, PM me for more detailed suggestions. I'm always happy to help out developers.
Good job!