Board + rack
Fifteen Z-layers encode the occupied cubes. Coordinates, rack letters, premium rules, and output schema are explicit.
15 × [15 rows × 15 columns]BENCHMARK CONTRACT
Nothing up
the model’s sleeve.
The test measures generation, not recognition. The model never sees a candidate list or solver trace.
One answer
The model returns only new `(x,y,z,letter)` placements in a strict JSON tool envelope.
play_move_3dExact score + rank
The validator checks legality and the solver optimum, then records the move’s tie-aware rank in the hidden top-20 window.
legal ∧ score = optimumTHE LATTICESpatial rules,
Spatial rules,
frozen.
CENTER
The opening word crosses cube (7,7,7).
AXIS
New cubes lie on exactly one of X, Y, or Z.
CROSSES
Each placed cube may form two perpendicular words.
PREMIUMS
A premium cube scores only on first occupation.
BINGO
Seven new cubes earn a 50-point bonus.
TARGET
Only legal exact-optimal single moves count.
RANK
Top-20 move rank is reported only as a diagnostic.
OUTPUT CONTRACT
Machine-checkable
by construction.
{
"tool": "play_move_3d",
"arguments": {
"placements": [
{ "x": 2, "y": 3, "z": 4, "letter": "A" }
]
}
}