Grim Nights [Steam store page]
The gameplay is okay but the pacing needs some serious work - it takes somewhere around 4 hours to beat the game on normal speed, and often after putting an hour or two into it you get mauled by a wave of enemies.

They aren't a slow progression, there are huge difficulty leaps, and there's really no warning or way to predict what you'll encounter next unless you've seen it before, so actually beating the game is a lot of trial and error.

I got about halfway through the game on my third try, but that's only because I grossly overstaffed my military and happened to have enough of the right units to wear down a boss before he tore through an entire line of watchtowers I had built.