3×3×3 LED cube.

Each horizontal layer shares its cathode connections while vertical columns carry the anodes. Selecting one layer and one column addresses an individual LED without requiring a separate controller pin for every light.

The tradeoff is the same one that later shaped the 10×10 matrix: multiple LEDs across different layers can create unwanted paths. The controller therefore scans the desired points quickly enough that separate flashes appear as one persistent pattern.

The cube was soldered one layer at a time. A simple jig kept the LED spacing consistent, and copper wire reinforced the structure when the layers were joined. Every LED was tested before the next stage because replacing a failed part inside the finished cube is considerably harder than fixing an exposed row.

• Use a jig; visual alignment is a mechanical problem before it is an electrical one.
• Limit soldering heat and test immediately after each connection.
• Plan structural wire and current limiting before committing to the final geometry.

Once individual points could be addressed reliably, the software combined rows, planes, and timed sequences into animated patterns. The display is modest, but it makes the connection between data representation, timing, wiring, and perception wonderfully direct.