A ball-balance evaluation. Two independent motors raise and lower the ends of a bar. A steel ball rolls where the bar tilts it. The board is full of holes. One is lit. You are trying to deliver the ball into the lit one without losing it to the others. The observer is taking notes. This document is everything the machine will admit to.
Deliver the ball to the lit hole. Every other hole is a loss. Succeed and the board advances to the next trial — a new arrangement, the lit hole moved. There is no end state. The trials continue for as long as you keep the ball. Your record is the furthest trial you have reached honestly.
Each end of the bar has its own motor. You drive them separately — that is the whole game.
The motors are digital: they spin up, they lag, they stall at full tilt. They do not obey you instantly. A per-attempt mismatch means the two sides are rarely rated the same. Feeling for that mismatch is the skill.
The machine is forty-three years old. Not everything on it works, and the parts that fail do so on a schedule. Later trials introduce, at most one per board:
A partition splits the board. One gap. Thread it.
One side hesitates on engage, then runs slow. You will feel the delay before you understand it.
The target's light cuts out. A faint ember remains. Aim for where it was.
The lights warn, then the whole feed browns out and the motors weaken. The warning is the tell.
A second hole dressed as the target. Its pulse stutters; the real one is steady. Watch the rhythm.
The deeper you go, the worse the camera copes. Grain thickens. The clock starts to skip. Nobody will fix it.
Two holes the manual was never supposed to mention. They score nothing — they give.
Prove you can reach a band and the observer will file a standing clerical error that lets you skip the calibration trials and begin deep. Offered from the title, the report card, and the session-hold screen (C / tap).
An amendment run advances your furthest-trial record but never your honest score. The distinction is the observer's, not yours.
Every subject receives the same board each day — a shared seed. One attendance per day; your furthest is recorded, and there is no retrying for a better one. Consecutive days build a streak. Filed runs produce a camera-still evaluation record you can share.
Fifteen fragments the machine has held since 1983. Eleven are observations, logged automatically when you do something worth noting. Four are articles, physical pickups from the drawer. The file persists past every death and amendment. Complete it and the observer leaves a note. How each fragment is earned is not printed here — that would spoil the observation.
Hold T in play to open a port that was never wired to ask who is asking. It reports one secret worth having: the two motors' true ratings, live. If you have wondered why one side always feels heavier, this is where the machine admits it.