The hanayama hourglass puzzle is made by combining two pieces each of two similar, but slightly different shapes. They are carefully calculated, with tricky movement added. It is impossible to unravel with one linear movement.
To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyzes reviews to verify trustworthiness.