Yavuz Demirhan is a prolific Turkish puzzle inventor with nearly150 published designs at Puzzle Will Be Played ( http://puzzlewillbeplayed.com/-/designer/Demirhan.xml ). Tetradyma is one of his latest and is unusual in that it requires four identical pieces to fit into a cube shape. It is also printable without needing any support material. I would rate it as tricky but not difficult - a great design to give to novice puzzlers.