This was fun! I played long enough to get two of my marines up to gunner level and then steam rolled everything haha!
I lost at my first attempt but soon got the hang of it.
I like the permanent death idea. That combined with the ability to level up soldiers is a nice mechanic. I'm sure I would have cried if one of my gunners died... However I never really got a taste of this. My first run I was overwhelmed by enemies and so lost my entire army before I had leveled any of them up. My second run I had 2 soldiers, used a couple of mercenaries on the first mission and obliterated the enemy as my soldiers leveled up. So I never felt the sting of perma death!
The music was great, the game play UI and controls were easy to pick up. I do think the UI could do with some improvements. It was not entirely clear how to place units whether it was drag and drop or click to deploy etc. And how to level them up. I didn't work this out till near the end of my first round. Although in hindsight clicking on them is kind of obvious!
One issue I had (on my losing run) was that units got a bit confused when there were too many enemies near. They got stuck changing targets constantly but not firing.
Also give me some more levels to play :)
Great job!