I found this delightful animation today:

The ball is traveling around a shape that can’t exist in our real world: the Penrose triangle. This illusion is the basis for some cool art, like Escher’s Waterfall. And I’m using it in my *Math You Can Play* books as a design on the back of my playing cards:

### Want to Play Around with the Penrose Triangle?

Here’s a few links so you can try it for yourself:

- How to Draw an Impossible Triangle
- Build a Penrose Triangle with Legos
- How the Lego Triangle Works (Impossible triangle in Perth, Australia)
- Or Make a Paper Model
- How I Made the Image for My Playing Cards

### Book Update

I’ve sent the first two *Math You Can Play* books to a copy editor (she edits the text part), so my focus this month is on finishing the illustrations and downloadable game boards. And designing the book covers — I think I’ll call this latest iteration done.

If everything stays on schedule, both *Counting & Number Bonds* and *Addition & Subtraction* should be available by mid- to late-spring. Fingers crossed…

Hint: If you are trying to build the Lego triangle, don’t use the yellow one above as a guide. I’m pretty sure that one is Photoshopped. Instead, look carefully at the red one after the cartoon here — a tricky change in a few small bricks makes the illusion work.