Cast Coaster is the brainchild of Serhiy Grabarchuk from Ukraine. He calls himself a metagrobologist. Interesting term, huh? Metagrobology is the study of puzzles and a metagrobologist practices or creates puzzles. Serhiy is the cofounder of Puzzlium Inc (www.puzzlium.com) - the first-ever puzzle social network. This puzzle mimics the appearance of a drink coaster. Its clean, flat design conceals the difficulty, making it an intriguing puzzle for beginners and advanced players.