X-Morph Defense is free on GOG today and you should get it.

[Mischief Maker]

Don't be scared off by the tower defense tag, it's closer in gameplay to Herzog Zwei.

Not only is it the superior maze-building form of tower defense, but when bosses show up it's like a twin-stick Raiden game.

It's REALLY good. To the point that I'm not sure if I'm sold yet on whether its followup The Riftbreaker is a better game.

[Jeneki]

X-Morph is awesome. So much destruction from beginning to end. I did a full play through without getting sidetracked to other games, which is always a good sign.

[BulletMagnet]

Just wanted to say a quick thanks for this; I probably would have ignored it if not for your recommendation. DLed it when it was free but just now got around to trying it, and it eased me in nicely; will definitely add it to the ol' backlog.

[Mischief Maker]

Glad you like it, it's the definition of "hidden gem."