Make: Volume 86

The Magic Blocks gadget cache is a fun and

simple “proximity and order” puzzle. It consists

of four gadget blocks. Each will illuminate a

single digit that you program into it — but only

when all four blocks are placed side by side, in

the correct order! Strategically located magnets

and magnetic switches are used to sense the

proximity of each block.

The four digits can be used as a code, or a

combination to a lock, or for any other purpose

you like in your geocache. You program each

magic block with the digit of your choice. Our kit

is fairly easy to assemble, requiring only basic

skill in soldering. We’ve designed a circuit board

and a ...