FUN.Great challenge for kids and adults.Want nowadays children away from long-time use of eletric screens?Try this set of puzzle cubes. | PATIENCE.Require lots of patience.But after research of these brain teasers,you will love the feel to conquer intelligence difficulties | Brain teaser cube puzzle toys DEVELOP children's abilities of recognition,imagination,hand-brain cooperation and communication | Difficulty levels of these interlocking puzzles: Medium to Very Hard.Enjoy the challenge! | Mind puzzle cubes really keeps your mind working.The quality of the item is actually very sturdy and strong.