The first letter of each paragraph is enclosed in a colored square. These squares cast a shadow on the page. The shadow is not the same for all chapters, perhaps suggesting different purposes for the various chapters.

Fifteen chapters have a thick shadow suggesting a light source coming from the top left corner: 2-3-4-6-9-10-11-12-13-15-16-17-19-20-21.

Chapters 7 and 8 have a similar shadow, but narrower, suggesting a light source again coming from the top left corner but positioned higher. Note that these two may in fact be slightly different, as the right side shadow of chapter 8 seems narrower.

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Chapter 1 has no source of light. The whole page is dark grey.

Chapters 5 and 18 have a thick shadow suggesting a light source coming from the bottom right corner.

Chapter 14 has a thick shadow suggesting a light source coming from the top right corner.

Finally, the letter on page 3 also has a shadow suggesting a light source coming from the top right, but this time the shadow is much more prononced on the left side, suggesting that the light source is not aligned with the top right corner.

Note: the clue card also has a shadow suggesting a light source coming from the top left corner.