Did you solve it? The shady puzzle that will keep you in the dark

Lightbulb moment. Illustration: Joe Hardy

Earlier today I set you the following puzzle:

Design a room with straight walls in which there is a position for a single light source that leaves either part or all of every wall in shadow.

Thanks to everyone who sent in responses. Many were correct, and they saved me the bother of drawing a solution myself...

My favourite design was the Room of Shadows sent in by Liam Roberts. Extra marks for the oriental rug, toilet, kitchenette, bedroom, and is that a wing for playing chess?

If you lived in this room, you would never leave. Illustration: Liam Roberts

I’m not sure there is any obvious way of solving this apart from doodling on a piece of paper and then realising that you will need to have a room that has ‘spikes’ sticking out from a main section. The simplest solution uses only six line segments, and is based on a triangle. It looks like a three-pronged shuriken.

@alexbellos pic.twitter.com/2WzrKAjdcc

— Nuno Ferreira (@zengra) February 1, 2016

A commendation to brothers Maksim and Filip Mijovic, staying in a hotel in Bristol, for submitting this solution with an actual lamp.

Bed, room. Illustration: Maksim and Filip Mijovic

The most popular reply was based on a square room. It’s the same idea as the triangle, but perhaps more room-like.

@alexbellos My y13 students have just come up with this solution pic.twitter.com/3iFWM3WrmJ

— NumBur (@burfordmaths) February 1, 2016

But why stop there!

Five star room Illustration: Andrew White

Six....

My shadow star @alexbellos pic.twitter.com/klPryIaOzP

— Jonathan Kendall (@jonintheuk) February 1, 2016

And 48, which Mike Welch calls the Icositetragonal Buzzsaw Room.

Saw the room. Illustration: Mike Welch

Most of the solutions were all symmetrical, but they didn’t need to be, which was another reason why I liked the Room of Shadows.

Thanks again everyone. It was really fun seeing what you came up with. Ill be back with another puzzle in two weeks.

This puzzle was adapted from one in Which Way Did The Bicycle Go? by Joseph Konhauser, Dan Velleman and Stan Wagon.

My most recent book is the mathematical adult colouring book Snowflake Seashell Star. (In the US its title is Patterns of the Universe.)

You can check me out on Twitter, Facebook, Google+ and my personal website.

And if know of any great puzzles that you would like me to set here, get in touch.