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using the new model JEV to play the game tetris
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Tetris where Jev picks every move from the seven legal options, but the game pre-computes landings, holes, roughness and a best plan so the model only ever judges outcomes.
User repository on GitHub
using the new model JEV to play the game tetris
Repo stats from the GitHub API, cached Oct 2026.
Tetris where every single move is chosen by TypeSafe's jev model. The game never decides anything. Each turn it sends the board state and a choice question over the seven legal moves, and plays back whatever jev picks. 363 pieces in, 114 lines cleared, zero holes. The panel on the right is the exact JSON sent to jev each turn, and its answer with the probability it gave every legal move.
Quoted from the project's README. Read the full README.
Watch out
The strategic ceiling is stated plainly: there is no memory between requests and no search beyond the current piece, so it cannot plan a setup or hold a well open across several pieces on purpose, and everything strategic it appears to do comes from which pre-computed facts it is shown. The prompt design is shaped by documented model behaviour - the jev-1.13 jaggedness notes say it is unreliable at counting, grids and arithmetic and that accuracy drops as irrelevant state grows - so the game measures every consequence in code. Only reachable targets are advertised: rows sealed under blocks are filtered out and each open dip reports which piece kinds still fit by simulation. Notable fixes were zero-slide placements, which the original lookahead made invisible, and landing depth rather than board height, which had silently punished filling a valley. Node 18+ and your own key are required, and no dollar cost is given for the 4.7M-token run. Copy reviewed against the repository README on 2026-10-04, not from running it.
Original write-ups on what this entry is for.
Posts from builders shipping with Jev right now.