Top Secret (puzzle of light - science toy)

As if straight out of da Vinci’s workshop, Top Secret is a spinning top that hides a secret message at the intersection of engineering & sorcery. Deciphered through motion, it functions entirely by geometry & light (LED & magnet are optional). Choose a premade design or add a custom message using simple instructions.

“…we were utterly amazed by this ingenious object.” -ESCAPETHEROOMers

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Setting Expectations

This is a naked-eye optical effect that relies on precision, so viewing conditions matter. If anything seems off, please reach out. I respond quickly, and most issues are resolved with simple lighting adjustments. Follow the instructions to achieve a result similar to the demo GIFs.

Reveal the Top Secret Message

For those with the insatiable curiosity of a true maker, profound wisdom lies within the print profile titled “Top Secret message.” Rumor has it that its whispers can be heard below.

The latest version has significantly improved clarity over what is shown in this video.

What's New?

This cipher leverages my pinhole tunnel technique to produce a miniaturized, naked-eye viewable illusion. This time, instead of swirling galaxies or infinity signs, scattered fragments mysteriously coalesce into a message. Give the top a spin and watch as seemingly random holes resolve into text with an animated marquee border, a direct outcome of the device’s precise geometry.

The latest version has significantly improved clarity over what is shown in this video.

How Does it Work?

You can read more about my pinhole zoetrope invention (at least I think I invented it) in the description of The StarCaster fidget spinner.

 

In short, miniaturization is achieved by combining the slits and images of a classic zoetrope into pinhole tunnels arranged in patterns. Light is only visible when these tunnels align between your eye and the light source. As the top spins, 16 animation frames appear in sequence, looping to create the illusion of motion.

What this cipher does differently from my earlier zoetropes is that it intentionally conceals its pattern by breaking it into fragments. Any single frame looks like just a handful of scattered dots, but when spun at full speed those fragments blend together through persistence of vision, and the hidden message springs into view.

 

I also wanted to preserve a sense of motion, so I added an animated border around the text. To keep it readable at the rapid speed of a spinning top, I used progression symmetry: with each rotation, every dot advances only to the next position in the sequence rather than completing the full animation all at once. This slows the effect to a comfortable pace.

Required Materials

This model is designed to work just with printed parts. For increased visibility, however, you may optionally use the following components. See the Bill of Materials section of this page for purchase links.

1. 1 Y Shape LED Light with Magnetic Control Switch – Cool White: The top is specifically sized to fit the one from Maker’s Supply.
2. 1 10x3mm round neodymium magnet: This is for the Cipher Key which is used to magnetically control the LED. The key is backward-compatible with my earlier zoetropes, but it uses a thicker magnet for improved reliability. While the LED also comes with its own magnet, that one is smaller and struggles to work at the required distance.

How to Customize

Now you can have your own secret message top!

Here's the whole process wrapped up in a short video. Written instructions follow below.

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For those who prefer written instructions, don't be intimidated by the number of steps below. I wrote it up granularly - each step is super quick. The whole process only takes a couple minutes. If you get stuck, please let me know so I can help and improve the instructions.

Process Overview

Since complex mesh operations can be slow, the process I am going to describe here is to generate the set of pinhole tunnels as its own object (using MakerWorld's “Customize” feature), and then to combine it (as a negative part) with the blank top in your slicer. While these instructions are targeted to Bambu Studio, they can easily be adapted to other slicers.

Step 0) Open the Pinhole Message Generator

Click the “Customize” button at the top of THIS page. It’s only on the MakerWorld website, NOT in Bambu Handy or Bambu Studio.

Step 1) Enter your message

By default the script will render in 2D so that you can tweak the text layout. As you edit options, click “Generate” to see the results.

 

You can have up to 3 lines of text:

• If you want just 2 lines of text, use the first & last lines. Later you can reduce line spacing (set to 0 or even negative).
• If you want just 1 line of text, use the last line. It won't be centered, but otherwise the spinning top will be top-heavy, likely making it wobbly & blurry. The slicer adds extra walls around the pinholes, and you want some of that mass to be down low for stability. If you must only have 1 line of text in the center, you can play around with infill % for the lower parts of the body, but it's easier to just use multiple lines.

Disclaimer: I'm not a font expert. I implemented the characters as a grid of up to 9x9 overlapping dots. If you don't like how a character looks, you can edit the definition at the end of the script.

Step 2) Adjust layout options

More space between letters tends to look clearer.

By default the script will show all animation frames superimposed, so the number of border dots will appear higher than what you set. This will take care of itself later.

Step 3) Optionally view the individual animation frames

This lets you see what each set of holes will look like individually. It's mostly intended for advanced use cases (e.g. you're tweaking my script), since it lets you check if pinholes have sufficient space between. When done, make sure to re-enable “render all frames.”

Step 4) Toggle the output to display pinhole tunnels

Remember to click Generate afterwards.

This step can fail if the server is busy, so you might have to try a few times.

Step 5) Download pinhole_message.stl

Make sure to choose the .stl download option, not the .3mf one.

This step can also fail if the server is busy, so you might have to try a few times.

Step 6) Download + open my “Customizable cipher” print profile (.3mf) in your slicer

Get it here (on this model page) - not from the script window. Make sure the customizable print profile is selected before you click the Download button.

 

Non-Bambu users, if you can't open the .3mf, you can directly download the blank top .stl. You'll have to rotate it to face down on the print bed.

Step 7) Add the pinhole tunnels to the customizable cipher as a negative part

Right click on the customizable cipher → Add negative part → Load…

Select pinhole_message.stl that you previously downloaded.

If your slicer warns that this .stl has non-manifold edges, in my experience you can safely ignore it. But if it bugs you, right-click on the part and select “Fix model” – the process takes about 30 seconds.

 

I know that this method works in Bambu Studio / Orca Slicer / PrusaSlicer. If, however, your slicer does not support negative parts, you can easily subtract the pinhole tunnel object from the cipher body in your CAD software of choice (e.g. Blender, Fusion, 3D Builder, etc.). In that case, just save as a single .stl file and then bring it into your slicer.

Step 8) Position the pinhole tunnels

Click the Move button and set the coordinates to be centered within the message area of the cipher. This is typically at object coordinates [0.00, 0.00, -5.00].

Non-Bambu users, to verify proper orientation, check that the axis anchors (tiny cones on the sides of the pinhole tunnels object) are pointing downwards. Other than for indicating orientation, these anchors won't affect the print.

Step 9) Save + print

See below for details.

How to Print

Download the print profile for the message you want or for the customizable version (see prior section for customization instructions). Each print profile includes all printable parts needed for the LED & no-LED versions of the top, and each plate is titled so that it is clear which ones you should print.

Cipher (top’s body)

• Use a dark PLA for the message area. The closer to matte black, the easier the text will be to read, but dark colors still work. Ensure the filament is high quality and dry since minor imperfections affect text clarity.
• This model is configured to print multi-color, but you can use the same filament for both colors if you don’t have multicolor capabilities. Alternatively, in the preview tab you can add manual filament swaps at layers 13 (1.4mm), 198 (19.9mm) and 298 (29.9mm).
• *Gently* buff out the tip if it feels jagged – otherwise the top will likely vibrate when spinning, making the text less clear. I usually just rub it against my shirt a few times until it feels smooth.
• The assembly video shows how to easily remove the support structure.
• Non-Bambu users, if using the .stl instead of my .3mf:
  • 0.1mm layer height, 0.2mm for 1st layer
  • Arachne wall generator, 3 wall loops
  • Concentric surface patterns
  • 10% sparse infill
  • Normal snug supports on build plate only, top & bottom z-distance of 0.2mm
  • To make multicolor, cut the model at these heights: 1.3mm, 19.8mm, 29.8mm
    (then assign colors to the different parts)

Light Diffuser

• Use a regular (not matte) white PLA for best visibility.
• I uploaded a separate print profile for an “unbalanced diffuser” in case your top vibrates due to its center of mass being slightly off kilter. This unbalanced diffuser slightly shifts the center of mass, and you can experiment with different rotational positions to achieve better balance. But start with the regular light diffuser as most tops should be well balanced as-is. Non-bambu users, if using the .stl instead of my .3mf, print this part with 100% infill.

Peg

• Only print this for the no-LED version.

Cap & Plug

• Only print this for the LED version.
• Each print profile includes two cap styles - just print one. v1 is slightly easier to spin evenly, since you can grip it lower. It's not a big difference and its peg is prone to snapping if the top is dropped, so I strongly recommend v2 (much stronger & sleeker).
• The assembly video shows how to easily remove the support structure.

Cipher Key

• Only print this for the LED version.
• If you already have a key from my earlier zoetropes, you can use it, but it won’t be as reliable because it uses a thinner magnet. I recommend printing this one.
• The print will pause at layer 20 (4.0mm) for you to insert the magnet. Carefully place it in the slot and make sure it does not protrude above the print surface before resuming.
• Non-Bambu users, if using the .stl instead of my .3mf, the pause height may differ - set at the top of the internal hole.

How to Assemble

I'd love for you to share a photo and/or story of the result in the comments. Seeing what people do with my work motivates me to keep putting out more free designs.

How to Use

• The less ambient light, the better.
• No-LED version: Shine a bright light into the top from close above as it spins. Try not to illuminate the front surface since the goal is to maximize contrast. A tightly focused flashlight is best but not absolutely required. The inexpensive yet highly effective one I use is the UltraTac K1 (affiliate link).
• LED version: Turn on by tapping the key to the cap. Remember to turn it off when finished since it won’t do so automatically. The LED has a few modes you’ll have to cycle through.
• Spin evenly and observe from the side at a perpendicular angle to see the hidden message appear. Try making a smooth deliberate motion with your hand. Text clarity depends on spin speed and angle. Practice makes perfect!

Video recording: While the effect is best viewed with the naked eye, it can be filmed using a slow shutter speed. The exact value depends on how fast the top is spinning, but I’ve achieved good results with shutter speeds in the range of 1/10–1/25 second (often labeled as 10–25 on many cameras).

Thank You

Though the optical mechanism is patent pending, Top Secret is always free to print for personal use (includes gift-giving).

 

To explore commercial use beyond my standard licensing options (such as props for escape rooms, exhibits, or other interactive installations) feel free to message me.

 

Shout-out to Coolified Gaming for inspiring one of the early message themes during my Reddit animation contest.

No affiliation with Top Secret Toys.

MembershipYou can always print this model for yourself or to gift, for free. Selling prints requires a tier 1 or higher membership. The allowed sales quantity is specified within each tier's terms.