Its really good, but it could use a few things.
All the atats explain themselves. But you need the following:
1. On game over, make an option to contine at a cost of energy credits. If you cant fork the credits, give tech.
2. have an area in the blood bank, to check your accuracy (average enemy's kiled with so so energy points), average amount of hits per 10 or so enemy's, how many of the items floating around are collected, and maby (if you find an approriate formula) your odds of surviving the next round!
3. Show how much money you need to get the next tech.
4. With Upgrade sentenial have another "buy sentenial" option. I may not have had enough money to do it so im unsure.
5. maby have bosses or somthing.
6. Have a sheild recharge upgrade
7. have a large energy capsul, that could give you 50 energy or so. or even a special one time capsule that could give you credits until you get hurt.
8. show a little line or timer until the next energy bank.
9. in the loader, maby have a legend to that the items in the game are, and maby a limited enemy directory.
With those suggestions, maby you could make another vesion. But yeah, the game was perfect, it was tough, fun, playful, had a unique theme, and interest facts. as a matter of fact, all your games have interesting facts.