Don't be fooled by my hours, I played the Non-Steam version quite a while.
A lot of people seem to be confused by this game. They probably expected some epic story mode or intense multiplayer battles, and end up disappointed because CC doesn't have these features. But it has something different: An incredible sandbox experience.
Do you want to know how I play it? I load up a map of Skirmish Defense, enable unlimited gold and that my brain can be placed anywhere, then build an unbreachable subterranean bunker and start the game. Now the real fun begins. Wave after wave of enemies will try to tunnel a way to my brain, but this task is a bit complicated by the fact that I constantly drop crates filled with pineapple grenades and molotov cocktails on their heads and watch their bodies explode into gore.
Soon, the whole battlefield is covered in body parts and debris. The never ending waves of enemies have to crawl trough a horrible mess of blood and flesh from their fallen brethren, only to be ripped apart by the next crate bomb. If this gets boring, I set up a Sniper with a high powered Anti-Vehicle rifle on a hilltop. It is just too damn entertaining to shoot a drop ships' engines out and then finish the remaining crew with a single, multiple-body-penetrating shot.
The completely desctructible environment is just so awesome to mess with. When you fire bullets at the ground, you can see them traveling through the dirt and coming to a halt. The game even takes into account what weapon was used - bullets of rifles will bury much deeper than the ones of pistols.
This also introduces some interesting mechanics in terms of bunker design. Depending on the angle from where the shot was fired, a bullet will either bounce off a wall or penetrate it.
Exploding grenades produce shrapnel that rips apart even the toughest enemy. There is even a Chainsaw Gun. Guess what it does. Yes, it fires Chainsaws.
Only problem with it are the lazy developers. This game has been in development forever, and nothing significant has changed. The devlog is updated twice a year max, and its been ages since the last release. This makes the 20$ pricetag feel like a rip-off, since you're buying an unfinished product that probably will never be finished.
If you can pick it up at sale, though... go for it!