I was sitting here watching the teaser we did and trying to put my finger on what was missing. I notice a while back that it wasn't quite right and I finally figure out what makes it so easy to play... Badies dont shoot at you! Sure the turrets fire and all, but they are easy to avoid/shoot.... but if I add the ability for baddies to shoot at you, then I suspect it'll get a lot more interesting! This means that even when a formation passes you by you still have to dodge and be careful.
I was also trying to remember what I needed to do on the weapons front, and I need to add a weapons power bar! Currently both bars are used as a shield and just make it look pretty; but what I need to do now is change the one on the right to be a weapon power bar! The idea is that this will decrease over time (or per-shot, Im not sure) and you need coins to keep it charged. Now I was thinking on the way to work today that if its over 1/2 full, then getting a full coin bar as well means you get a new power up, while if its under 1/2 full, then you only top up the current weapons power! If the bar runs out, then you drop a weapon level and the Bar starts again.
This means you WILL have to get into the thick of things to just to keep your weapons powered up, or else you run the risk of powering down to a pea shooter again! (in theory)