Sang-Froid: Tales of Werewolves belongs to the rather uncommon action/tower defense hybrid genre, it differentiates itself by pinning the player against fewer, stronger enemies that require the use of particular weapons or traps to take them down, all of which cost money and time, both in limited supply. This helps create a feeling of helplessness which I found made me take planning before a level more seriously and helped me immerse myself in the experience.
To add to this feeling, the map is also a lot more organic than what you see in Orcs Must Die! or Sanctum, featuring forests, frozen rivers and other natural barriers. Even sound and, impressively, the wind play an important role while playing. Also, I would be amiss if I didn't mention the story because it's very good for a video game and a rare sight in the genre.
Overall, I really enjoyed my time with this game and I wish I had known about it sooner. Also, it's complete free.