About the rank exam
The rank exam is a ladder of eleven computer opponents. The 10 kyu examiner sometimes plays on a whim; higher ranks search deeper and waver less. From 1 dan up they think on the clock and read the endgame to the very end.
There is no grading during the game. Afterwards, “Review this game” grades every move and explains the mistakes — reviewing a failed exam is the fastest way to the next pass.
Alongside the ranks, a new Master of the Week takes over every Monday. Each of the five Masters has a habit — one grabs corners, another flips as many discs as it can — and plays at about 2 to 1 kyu. Spot the habit and turn it against them. Beat the Master and you get a victory certificate with the Master's seal. Games against a Master do not count toward your rank.
The eleven examiners
| Rank | Reads ahead | Reads to the end | Wavering |
|---|---|---|---|
| 10 kyu | 1 move | from 4 empties | 60% random, else ±4 discs |
| 8 kyu | 1 move | from 6 empties | 35% random, else ±2.5 discs |
| 6 kyu | 2 moves | from 6 empties | 15% random, else ±2.2 discs |
| 4 kyu | 2 moves | from 8 empties | ±1.2 discs |
| 2 kyu | 3 moves | from 10 empties | ±0.7 discs |
| 1 kyu | 4 moves | from 12 empties | ±0.4 discs |
| 1 dan | up to 6 moves (1s per search) | from 12 empties | none |
| 2 dan | up to 8 moves (2s per search) | from 14 empties | none |
| 3 dan | up to 10 moves (3s per search) | from 15 empties | none |
| 4 dan | up to 12 moves (4.5s per search) | from 16 empties | none |
| 5 dan | up to 16 moves (6.5s per search) | from 18 empties | none |
“Wavering” is random noise the examiner adds to its score for each move (±4 discs means anything from −4 to +4 discs is added). Once it is reading to the end, it adds no noise and plays the best move (the share of random moves stays the same, though). From 1 dan up, the time in the table is how long each examiner may spend on one search. Once it reaches the empty-square count where it reads to the end, it first tries to read to the end; if that search runs out of time, it runs a second search of the same length and plays the best move found at the depth it reached. On those moves it can take up to about twice the time shown. So that no two games are the same, while more than 50 squares are empty (the first 10 moves of the game, both sides together) they read 4 moves ahead with ±0.25 discs of noise.
Where to start
If you are new, start at 10 kyu. That examiner plays 60% of its moves at random, so focus on taking corners and not giving them away.
From 4 kyu there are no random moves, and the noise shrinks as the ranks go up. From 1 dan the examiners think on the clock and read to the end from 12 empty squares.
If you keep losing, go back to whatever beat you. Lost the corners? Read “Corners, X-squares and C-squares”. Overturned in the endgame? Try “How to read the endgame” and the endgame puzzles. After any exam, “Review this game” shows which of your moves were mistakes, one move at a time.