An optical illusion afghan or wall-hanging.
You may see pyramids rising up, holes you can fall into, boxes moving away from you, or many other things, depending on where you stand.
The pattern is very easy to follow and can be adapted in many ways. The afghan in the photos was made in DK yarn but you can use any yarn of your choice. You can also change the overall size. The pattern includes several ideas for changes. One of these even allows you to use up lots of oddments of yarn. A colouring-in sheet is included so you can plan your own design.