I Tried Making a Pen Plotter to Draw Maps of the Moon

Sebastian Lague details a homemade pen plotter built to draw spiral cats and contour maps, with the Moon as the main test case. The project starts from the mechanical side — base, belt assembly, stepper inspection, motor driver, and pen holder — before moving into the software and motion-planning problems that make the machine actually useful.

For developers, the interesting part is the pipeline from data to motion: line drawing, random walks, marching-squares contours, smudge fixes, and path optimization. That mix makes the project relevant to anyone working on toolchains, procedural generation, or robotics-style control, where the hard part is often not the algorithm itself but getting clean output from real hardware.

The finished plotter is used to produce Moon maps, then extended to Mars and Earth plots, which gives the build some nice range beyond a single demo. It’s a compact reminder that even a small desktop machine can become a good testbed for geometry, scheduling, and precision movement problems that feel familiar to game tech work.