Grid Lookup

This puzzle starts with an image that has a grid on it. The image is often a map or floor plan, but could really be anything. The important part is that a letter (or number) is assigned to each horizontal and vertical location of the grid.

The second part of this puzzle is a clue that suggests pairs of letters (or numbers).

The puzzle is solved by recognizing that the pairs can be used in reference to the rows and columns of the grid. In this example, the pair B-L references the map row labeled B and the map column labeled L. The grid block corresponding to this row and column has a 5 in it. Repeating with the remaining pairs, we get grid cells with the numbers 4, 6, and 5, respectively. This gives us an overall code of 5464.

The puzzle formed in this way is fairly straightforward. To make the puzzle more challenging, make the pairs of letters less obvious. You can do this by providing a list of two word phrases. The phrases alone do not make sense. The trick is that the first letter of each word refers to a row or location in the grid. For example, consider the list below.

The first letters of each line are B-L, F-N, C-M, and D-I, which provide the same lookup as before.

Invisible Ink

A simple way to hide a message is to write it in invisible ink. For a few dollars you can get a pen that writes in ink that is hard to see but reacts to ultraviolet (UV) light.

The other part you will need for this puzzle is a UV light, also known as a black light.

The black light is given to the players, and the players have to shine it on the correct object. Words written on objects will be invisible until players reveal it with the black light.

Invisible ink pens are sold with different colors. I recommend using “yellow” invisible ink pens. Other colors I tried were slightly visible under normal light, which made them unusable for the puzzle.

You may have to experiment a bit on what you can write on. For example, I find I cannot write on a printed image because the pen will smear the printer’s ink just enough to see it. Different types of paper may work better than others. That said, give the ink a little time to dry before deciding it is too visible.

Paper Segment Display

The decoder device in this puzzle is a piece of paper with holes cut into it that form some or all of the bars in a seven-segment display.

In my example here, I have cut only 6 of the 7 segments as the none of the numbers in the code I am using need that segment.

The other part of this puzzle is the coded pattern.

Neither piece of the puzzle makes sense on its own. But when the template is placed on top of the coded pattern in the correct positions, numbers are revealed.

As can be seen in this example, the correct code is 3594.

When creating the coded pattern make sure there are enough cues for players to know how to align the decoder template on the pattern. The decoder must be placed precisely to reveal the correct number. In the example here, you will see that there are boxes to show where to place the decoder and an arrow to define which way is up on the paper.

The patterns for this example are posted here.

The example here has one decoder number that has to be moved to multiple locations to reveal all the numbers. An alternate approach could be to create a template decoder that has holes for all the numbers together. This would mean that placing the decoder in one spot reveals all numbers. A fun change to this puzzle would be to have the holes in the decoder form one set of numbers, but when applied to the code pattern, a different number is revealed.