Features
The Square 1 consists of three layers. The middle layer contains two halves, while the top and bottom layers consist of big corner and smaller edge pieces, which appear as different shapes.
Function
You can horizontally twist the Square 1's top and bottom layers. You can also twist it vertically, but only if all the top and bottom pieces line up with the two halves of the middle section. Because the pieces have different shapes, the shape of the whole puzzle changes as you work it.
Tutorials
Many tutorials for the Square 1 use algorithms to describe the solution, making them a little hard to follow if you are not familiar with this kind of notation. Some of them have detailed illustrations, however, making them easier.