I trained a tiny 14M-parameter world model of 2D Minecraft in <10 minutes on 1xA100 (~10 cents on google colab). It runs locally in your browser, so you can play on your phone. It requires WebGPU: Chrome, Edge, or Safari on iOS 26 (built a custom runtime to save memory).

There's also a benchmark to score your own models: beat 0.562 and the site switches to your model. Memory is the open problem: walk 10 tiles away from your table and back, and it's gone.