Qr Construction

In a home DIY escape room, you can leverage the internet by directing players to content on their mobile devices using QR codes. As a reminder, a QR code when scanned with a mobile device’s camera can direct bring up a particular URL. There are plenty of free services to create a QR code from any URL you choose,

A QR code can be posted on just about any object, and sometimes QR codes can be parts of items in the room. But alternately, you can make the building of QR codes part of the puzzles.

The basic idea of these puzzles is to provide parts of a QR code that have to be put together in some way. Essentially, these puzzles break apart or otherwise mangle a QR code, and the players have to put it back together. Before we talk about how to mangle QR codes, it is helpful to be familiar with what changes will not break a QR code and which will. This is important as the design of a QR code construction puzzle involves breaking the QR code and having the player fix it.

Changes you can make to QR codes

QR codes are designed to be quite resilient to change. Because they are designed to be scanned from a camera, they are readable in the face of noise and misalignment. Thus, it is possible to rotate the QR code or even flip it upside-down and it will still work.

Not surprisingly, the QR code can be sheared in the same way that might happen if the camera is not held perfectly straight.

Surprisingly, QR codes can be mirrored and will still work.

There is redundancy in a QR code’s data, and they still can be read when certain parts are covered up. In particular, the center part of the QR code is redundant, and it is common to place a logo there.

It is also possible to blend a QR code with another image as long as there is enough contrast between the 2 colors of the QR code. This can be particularly helpful for QR construction puzzles as it gives hints to users on the proper orientation of the image pieces.

Changes that break QR codes

As resilient as QR codes are, once you break off a big enough piece, it will no longer be readable. When making a QR construction puzzle, you want to force the players to put together all of the pieces before it can be scanned.

When you look at a QR code, you will see “eyes” in three of the corners as well as a smaller alignment eye in the fourth corner. QR scanners use these elements to register the position of the code, and removing any of them will make the code unreadable.

An interesting vulnerability of QR codes is that the matrix of squares has to be precise. In the following example, the left image splits the two halves of the code by a small amount. The right image shifts the two halves a little bit vertically. Despite the changes being very small, they render the codes inoperable. This means once you separate the QR into pieces, it needs to be possible to align them again precisely.

Puzzles

With that in mind, here are some puzzles based on putting together QR code pieces.

	Jigsaw QR Make a jigsaw puzzle by cutting a QR code that players must reassemble.
	QR Fold In Complete a QR code by using simple Origami folds.
	QR Cube Solve a 3D rotating cube puzzle to expose a QR code.
	Fold Back QR A sheet of paper must be folded backwards to line up a QR code.