I think you should be able to sell towers for a 100% refund before you start the round, and when you set a new rally point you should be able to see the current one to be more precise. Otherwise, outstanding.
Found a glitch: in the starting area, (before you can go past the guard blocking the fence) if you run all the way to the left you can slip past an opening between the end of the fence and the rock wall that ends the map. + this up to get it fixed.
There needs to be a "Go back to the menu" button, so if I'm trying to reach 100,000 points and my combo breaks on level 5 i can do it without refreshing out waiting for bullets to kill me.
Sorry to double comment, but the corpses of the juggernaut, (multi-sawed death machine) the flying double-propeller machine, and the blue and the orange mini-spaceship looking things don't disappear. Is this because they're all machines? Anyway the newer machines can blend in and it's hard to tell at a glance which ones are dead or alive. Also I'm pretty sure they overlap new bonuses on the ground. Its pretty annoying, is it a bug? Thanks. (Maybe this is my third comment?)
Can you add a way to distinguish between guns? I don't know which is which and having to switch while being charged by a spider is annoying. Maybe you could add a menu of what guns you have? And also what guns you have left to unlock so I can know when to use which perk.
People have to stop complaining about how the engineers can't turn. In the Post-Incident Report, Day 1: "You couldn't even see out of that escape suit." I'm guessing they managed to alter the suits to give them a small line of sight. They are turning, but it doesn't look like it cause they appear so big. However, the people's sizes compared to the ship size doesn't make sense. They couldn't have made it so far away from earth in a teeny saucer like that. So, the people are enlarged to easily be placed. The battlefield is huge as well, would you turn to the side to fight while a massive horde of aliens ran towards you?
In a defense mission you can move a second before your enemy attacks. In this way you can pull your hero back right as your opponent swings, leaving it nonmoving and you unscathed.
I found out a way to toggle E, to always see the gun ranges. Press and hole E, then click outside the game. Let go of E. The white ranges should still be there. Then click back in and they remain and you can continue playing.