🎮 Gallery
One model, one prompt, ten games. Every tile opens that game on the demo with the model playing; the number
under each is its score against the teacher (1.00 = matches the teacher, 0 = random play).
🏆 Scores
16 held-out episodes per game, argmax move, episodes capped at 1500 steps. Random play and the teacher run the
same seeds through the same harness. vs teacher is (model - random) / (teacher - random), so 0 is random
play and 1.00 is the teacher. In the chart the light bars are behaviour cloning and the first DAgger round, the
dark bar is this release.
Table with columns: Game, Random, PlayJev, Teacher, vs teacher| Game | Random | PlayJev | Teacher | vs teacher |
|---|
| 👾 Space Invaders | 215 | 400 | 400 | 1.00 |
| 🏎️ Racer | 238 | 6707 | 6712 | 1.00 |
| 📦 Sokoban | 6.6 | 102.1 | 102.2 | 1.00 |
| 🐍 Snake | 1.0 | 89.5 | 114 | 0.79 |
| 👻 Pacman | 113 | 3702 | 7026 | 0.52 |
| 🍄 Infinite Mario | 613 | 1764 | 4229 | 0.32 |
| 🧱 Tetris | 162 | 4718 | 15288 | 0.30 |
| 🐦 Floppy Bird | 0.0 | 13.8 | 84.0 | 0.16 |
| 🧊 Breakout | 496 | 2712 | 16547 | 0.14 |
| 🔢 2048 | 1021 | 3386 | 19593 | 0.13 |
| mean | | | | 0.53 |
🧠 How It Decides
The model never sees a game's name. It sees the current frame and the list of moves, and it answers with one
of them.
The input is the current frame and the list of moves, rendered with the frozen OpenJev prompt. The answer is
the single token after Answer:, and the probability over moves is the softmax over the option letters at
that position: one forward pass, no sampling, nothing generated. Moves are shuffled in every training sample,
so position carries no information. Where velocity matters the vision tower also takes the previous frame, at
no extra token cost.
The demo's single game view is the whole model in one picture: the frame on the left is the only input, the
bars are what the forward pass returns, the line below them is how sure it was at every step so far.
from playjev.model import PlayJevModel
model = PlayJevModel("OmniJev/PlayJev-0.8B").load()
d = model.decide([frame], options)[0]
d.choice, d.probs, d.confidence
The prompt, the readout and the option format are built in
playjev/model.py, and the demo prints the exact
prompt for every game.
🏋️ Training
One program per game (BFS, expectimax, placement search, A* with deadlock pruning, physics search) plays on
the game's internal state and labels frames with a soft target. The model trains on 863k such frames, then on
two DAgger rounds where it plays 40k frames per game and the teachers relabel what it visited. Full
fine-tuning, one epoch per round, batch 64, learning rate 2e-5, fp32 master weights with bf16 autocast.
The trainer is playjev/train_sft.py.
🔭 Open Problems
- 🏃 Motion (Breakout, Mario): one still frame carries no velocity, so the previous frame goes in as a second image.
- 🎯 Single-step precision (Floppy Bird, Tetris): the move that decides the episode is a few hundred frames out of 40k.
- 🔍 Tile digits at 448 px (2048): relabelling cannot help where the digits are unreadable, resolution can.
- ⏱️ Latency: at 83 to 100 ms per step the decision lands one step late, and training on labels shifted one step buys part of it back.
📄 Licence
Apache-2.0, same as the base model. The ten games are other people's work and stay in the code repository
under their own licences.