The eleven computer opponents and how each one plays

What separates Téo from Ingrid: how far each computer opponent searches, how far it wanders, what it values, and what each one can teach you.

Every name on the computer list under Play is a character played by this site's rules engine. They are not people and they are not accounts. The portraits, flags and one-line biographies are invented, and no real person is portrayed.

The number beside each name is a label for roughly how strong those settings are, not a measured rating. It has not been calibrated against players here, so beating the 1460 does not make you a 1460 player. Games against them run in your browser and change no rating.

What really differs

Each character is a handful of search settings, listed below in the tiers the play screen uses.

Depth is how many plies the search may look ahead, a ply being one move by one side, within a budget of positions that runs from 2,000 for Téo to two million for the engine. Captures waiting at the end of that horizon are always played out.
Window is how far from its favourite move a character may wander. It picks at random among the moves scoring that close, and the window is given here in men.
Random moves are deliberate slips. Now and then, when it has a choice, it plays any move except its favourite.
Values change what it likes: a king, free squares to step to, men kept on its back row, and a bonus for each of your pieces it removes.

Just learned

Téo, 620. One ply, a window of four men, 15 random moves in a hundred. Each piece of yours he removes earns a bonus of 0.9 of a man. Play him to learn how the pieces move and what compulsory capture does to a game.

Mia, 720. Two plies, a window of 3.2 men, one random move in ten. Her back row is worth up to 0.4 of a man, more than to anyone but Hugo, yet a window that wide swamps it. Use her to try ideas and make your first kings.

The square

Seu Nildo, 1040. Three plies, a window of 1.8 men, one random move in twenty. His capture bonus of 0.7 is second only to Téo's. Counting starts to pay here: work out both sides of an exchange before you offer one.

Gus, 1130. Four plies, a window of 1.4 men, three random moves in a hundred. He gives free squares more weight than anyone else in this tier, so practise keeping your own men able to move.

Amara, 1210. The same depth and slips as Gus with a tighter window, 0.9 of a man. She has a capture bonus of 0.45 and puts no value at all on her back row, so expect trades and aim for a king through the squares she leaves.

The club

Katya, 1460. Six plies, a window of 0.4, one random move in a hundred. She prices a king about 31 percent above the default, the highest on the list, so giving men for a king looks better to her than to anyone else. Keep men on your back row, because that is where she wants to crown.

Hugo, 1540. Six plies, a window of 0.3, the same slips as Katya. His back row is worth up to 0.7 of a man, the most on the list, so a man leaving it costs him more in his own reckoning than it costs anyone else. Use him to practise opening a way to your king row when the defender values every man still on it.

Dao, 1620. Seven plies, a window of 0.2, one random move in two hundred. Each free step he has over you counts 0.08 of a man, more than any other character gives it. Keep count of the moves you have left, because the game ends the moment you have none.

American checkers, Black to move: square 9 is taken and the jump over it would land on 14, which is taken too, so Black's one man has no move and White wins.

Masters

Ingrid, 1870. Nine plies, a window of 0.1, no random moves, and no value that stands out. She will not hand you a slip, so practise having a plan.

Youssef, 1980. Ten plies, no window and no random moves, so he always plays the move his search prefers, with a small capture bonus of 0.25. Practise counting a long capture sequence before you start one.

The engine

The engine, 2300. Twelve plies, no window, no random moves, and the evaluation exactly as tuned, with no character on top. Use it to test a plan. When the game ends, press Download PDN, open the file and paste its text into the analysis board to look for the moment the evaluation turned.

One position, eleven answers

American checkers, White to move: 26-23 gives up a man, Black has to capture with 19x26, and 31x22x13 takes two men for one, leaving two men against one.

Each character's own settings were run on this example position 2,000 times, with a different random seed each time. Téo chose 26-23 about three times in ten and Mia a little under one in four. Seu Nildo chose it nineteen times in twenty and the next five a little more often. Ingrid, Youssef and the engine chose it every time. One position proves little, but it shows what a window and a random move do, and that once the man is offered nobody has a choice: the capture is compulsory for all eleven.

Choosing who to play next

Choose by what you want to practise rather than by the number. Stay with one name until you win more games than you lose, then try the next. Neighbours can need different plans: Katya and Hugo share a depth and nearly a window, yet one pays high for kings and the other for his back row. All eleven play all four rule sets, so changing the rules is a fresh problem against a familiar name.

Pick your next game on the play screen. If the position above appealed to you, forcing captures shows how to find more like it.