A couple of years ago I played/solved all of the Cannibal Monsters challenge levels. It's a bit like peg solitaire where one Monster must be left.
In Cannibal Monsters - the physical game, and now Monsters Survival of the Fittest, the objective is the same. The rules of how one monster eats another is based on colors. A bit too awkward to explain without images. The last few days BlogSpot has been giving me a hard time with this.
Suffice it to say, just about everything Raf Peeters does at Smart Games, is challenging and fun! Last month I reviewed their update of Titanic.