I have NEVER spent so long playing a flash game before.
Classic RPG plot, wrapped around gradius style gameplay, which sounds absolutely ridiculous, but ends up FANTASTIC.
Someone needs to put this guy in charge of a full scale project with a team.
good start. Couple of things to mention though.
1. main gun is insane over powered. It's the only gun you need.
2. having the 5th towers rage increase on each upgrade is a bit pointless due to the fact that it already is capable of covering the entire path
3.The damage per second of your towers might need a bit of tweaking, since it costs less to upgrade the main gun to upwards of 10,000 DPS than it does to upgrade the 3rd tower to 5,000 DPS