I love this! The way you've expedited energy management with the mouse click, is really smart. It's like a real time FTL in that way. And I know this is already really polished, so you don't need really large concepts for implementing, but... you know.... :)
I think it'd be really cool if you emulated elements of basic circuitry. Like you already have the mouse-click-energy-storage acting as a capacitor. But if you had to buy resistors for certain guns that needed smaller amounts of energy, or charge a battery to fire a really big cannon, or attach knobs to control the amount of energy going to a light or something, I think it would be really cool.
Take it or leave it, either way this is still really good.