This online Square-1 simulator unfolds the puzzle so you can see all pieces of the top and bottom layers, even the ones in the back. The middle layer is visible from only one point of view because the front position determines its shape. The middle left piece is always in a fixed position, only the right side is moving when you do a slice.
Notation of the Square-1 puzzle
You can manipulate the puzzle with the arrows or you can do the same twists and turns with the buttons below the Scramble / Reset buttons.
Q - up inverted
W - up
A - down inverted
S - down
E, D - slice
The program allows you to rotate the upper and bottom layers in one twelfth steps aka 30 degrees in two directions, and can make a sclice move if the thicker corner pieces allow this in the upper and bottom layers and they don't block the puzzle. Don't try the drag and drop because it's not working yet.