The problem this solves is a fun one: how do you fit a working planetarium onto a chip with a very small amount of memory and no native graphics stack? The maker's answer is picostellar, a sky-viewing app written in CircuitPython that runs on the RP2040 and draws roughly 8,400 stars plus every one of the 88 constellations. It even works out where the Sun, Moon and planets sit for any chosen place and moment.
Getting there took some clever engineering. The star data comes from the Yale Bright Star Catalogue and fills about 90 kB, reaching down to magnitude 6.5. To make Python fast enough, the maker wrote picogame, a rendering module that draws without a full-screen framebuffer, and turbo, which turns the performance-heavy functions into native machine code. A third piece, xip_map, reads files straight from flash instead of pulling them into RAM. The result is a complete redraw of the whole sky in roughly a tenth of a second on a 320x240 panel, with individual frames landing somewhere between 39 and 78 ms.
What stands out to me is the control set. You can pan across the sky, zoom, and slide through time, and the circular view shifts from night into daytime blue as you scrub, with the Sun and inner planets appearing. A menu toggles constellation lines, star names, the ecliptic, a guided tour and a red night mode, and a reticle names individual stars with their constellations and magnitudes. It has been shown running on a Raspberry Pi Pico, a Fruit Jam RP2350 board over HDMI capture, and a Picopad Pro handheld, using that console's D-pad and buttons.
The open question is the hardware ceiling: with only 264 kB of RAM on the RP2040, I wonder how far the catalogue could grow. Everything is open source with a ready-to-copy CIRCUITPY folder and a browser demo, so it seems easy to judge for yourself.