I gave DeepSeek one prompt and it built SATELI, a live 3D satellite tracker that runs in your browser. No orbit libraries, just three.js for the 3D.

Try it: sateli-deepseek.vercel.app How I ran it: Harness: AgenC Core Model: DeepSeek V4.1 Flash (deepseek-flash), max effort Permissions: "never asks", so it worked on its own from start to finish One prompt, one try Cost: about $1.52 for the whole session at DeepSeek's standard prices. It ran in off-peak hours, which DeepSeek bills at half price. 99% of the input tokens came from the cache. What it does: It shows all 16,846 active satellites moving in real time on a 3D Earth, with the real day and night line and city lights on the night side. 11,157 of them are Starlink. Set your city and it tells you when you can see the ISS and other bright satellites from where you are: start time, direction, how high it gets, and a countdown. It draws each pass across a chart of your sky, and a night vision mode turns everything dim red so you can use it outside. The part that impressed me: It wrote SGP4, the standard model for satellite orbits, from the published equations. Then it tested it against the official verification cases (Vallado et al., 2006). On all 666 test positions across 33 satellites, its output matches the reference to within 8 micrometers. SGP4 itself is only accurate to about a kilometer in the real world. What the test proves is that DeepSeek's implementation matches the reference one. It also compared its ISS position with an independent tracker, wheretheiss.at , and the two were about 2 meters apart. The satellite data comes from CelesTrak's public feed and refreshes in your browser once it is more than 6 hours old. No account, and your location never leaves your browser. Disclosure: I build AgenC github.com/tetsuo-ai/agenc-core and love deepseek