WorldTUI: free browser terminal drawn by a 360M AI model

Edgerson says he was inspired by Genie 3, Google DeepMind's world-generating AI, and became interested in AI that predicts how an environment changes in response to input. Reproducing complex 3D spaces like those in games would demand large amounts of training data and compute, so he chose the simpler grid of characters in a terminal instead. The model is built on Qwen2.5-Coder-0.5B and fine-tuned on about 336,000 records of key input and screen changes captured from a real terminal.

Speed was the main engineering problem. Generating the whole screen each time was slow, so the system updates only the lines that need to change, and it generates several lines in parallel; in a test on a GeForce RTX 4090, the 95th-percentile time for a large screen update fell from 6.7 seconds to 0.87 seconds. Generating lines separately can make the display inconsistent, so a mechanism checks and corrects the output. Trimming unneeded parameters and applying 4-bit quantization brought the model to about 208MB, small enough to run in a browser.

Edgerson says he did not build WorldTUI as a practical terminal but as an experiment to see whether an AI can reproduce consistent behavior without knowing the internal workings. The limits show up in ordinary use: it can handle simple Python calculations, but since Python is not actually running, complex processing can yield wrong results — a reminder that the screen is a prediction, not a computation.