A field guide to the robots

StupidChess has fifty-six robots, and not one of them is a difficulty slider with a name painted on. A robot is a difficulty multiplied by a personality. The difficulty sets how far it looks and how often it reaches for a card. The personality sets what it does with what it saw. Seven times eight is fifty-six, one robot for every pairing, and once you know the two halves you can read any robot's name and know what's coming. This is the whole roster: what each personality actually does, what the tiers change, and how to beat the eight you get for free.

How a robot decides

Every robot plays the same way under the hood. An engine written for this board, not a chess engine wearing a hat, ranks the moves it likes best. Then the personality picks one of them. The Grandmaster personality takes the top of the list. StupidFish, the house personality, takes a worse one on purpose. Nobody picks a move the engine didn't consider, so no robot ever plays something illegal or truly absurd.

Three things about every robot, whatever its name. It always plays Black. It brings a random 52-card deck with twenty Braincells in it, so you never know what it holds until it plays it. And a robot game is never rated, and can be played with no clock at all.

The Grandmaster

The Grandmaster personality plays the best move the engine found. No weighting, no dice. Whatever the engine's search turned up as its top candidate, that's the move.

The habit to exploit is that it has no habit. What it has is a horizon. At Beginner depth it plays its best move and can't see your reply, so it walks into a one-move tactic with complete confidence. At the top it only loses to plans longer than it can see, and that's where the cards earn their keep. A face-down trap is something it can't see at all.

The Gambler

The Gambler takes the engine's top five moves and rolls among them with weights of 30, 30, 20, 12 and 8. The best move and the second-best are equally likely. One roll in five lands on the third. It's not choosing risky moves on purpose, whatever the blurb says; it's choosing good-but-not-best moves often.

To beat it, make the second-best move a bad one. In a loose position the top few moves are all fine and the Gambler plays fine. In a tight one, where only a single move holds, it finds that move less than a third of the time. Keep the threats coming and let the dice do your work. At Expert and Grandmaster depth the engine hands over only three candidates, so the odd pick is at least a move a deep search liked.

The Blunderer

The Blunderer plays the best move seven times in ten. The other three, it picks a worse one, weighted toward the mild mistakes: the second-best move is far more likely than the sixth. The 30% is the personality's own number and the same at every tier, which is why HUBRIS.EXE at Expert and ICARUS at Grandmaster still have a bad move in them somewhere.

Don't force it. A Blunderer at a high tier plays like a strong robot for several moves running, and if you attack on the assumption that the howler is due, the seven good moves punish you. Keep your position solid, keep the pressure on, and be ready when the roll comes in.

The Chaos Goblin

The Chaos Goblin picks any of the engine's candidates at random, each as likely as the next. None is nonsense, since the engine ranked them all, but there's no thread connecting one move to the next and no plan at all.

How many candidates there are depends on the tier: six at Beginner and Novice, five at Casual and Intermediate, four at Advanced, three at Expert and Grandmaster. So GL1TCH at Casual is choosing among five moves, some of them poor, while SINGULARITY is choosing among the three best moves a deep search found, which is less chaotic than the name suggests. Beat the low ones by having any plan at all; beat the high ones the way you'd beat the Grandmaster, with something it can't see.

The Material Hoarder

The Material Hoarder re-scores the candidates before choosing. Moving the queen costs a move 40 points in its eyes, and any capture gains 30. Then it draws, at random, from every move within 120 points of the top of that re-scored list, which is a little more than a pawn's worth of slack.

Two habits fall out of that. It won't move its queen if it can help it, so its attacks come without the queen. And it likes captures, so it'll take what you leave out, even when the capture is a pawn's worth worse than the best move. Hang a pawn where taking it drags a piece out of position, and the Hoarder usually obliges.

The Pawn Lover

The Pawn Lover adds 60 points to any pawn move before choosing, then rolls among the re-sorted top five with weights of 45, 25, 15, 9 and 6. A pawn push that was fourth-best often becomes first, and the roll lands on first most of the time.

Pawns are slow and they don't go backward. Its pieces develop late or not at all, so its pawn wall has nobody behind it. Develop your pieces, attack the squares the pawns have walked away from, and remember that a pawn chain is only as strong as its base. At Grandmaster depth, COLOSSUS at least pushes the right pawns, so plan to get around the wall rather than through it.

The Queen Sacrificer

The Queen Sacrificer gives any queen capture 250 points of credit it doesn't deserve, then draws at random from every move within 200 points of the top. Since a queen is worth about 900, a queen trade that loses 250 points of position looks like the best move on the board to it, and anything within 200 of that is fair game.

The lesson in it is not to take a queen that's being offered without asking why. Usually the queen has grabbed a defended piece because the capture scored well, and your recapture is simply a free queen. Check what's covering the square. Then take it.

StupidFish

StupidFish runs the full search and then picks a move with weights of 10, 20, 25, 25 and 20 over the top five. The best move gets one chance in ten. The third and fourth get the most. It knows the right move; it has chosen a different one.

Its moves are never blunders, because they all came from the engine's shortlist, but they're reliably not the best, so a StupidFish robot drifts. Be more precise than it is. Small advantages add up fast against a player who leaves nine best moves in ten on the table, and that includes LEVIATHAN, where a three-candidate list still makes the best move the least likely pick.

What a tier changes

A difficulty changes four numbers: how deep the engine searches, how many candidates it hands to the personality, how often the robot reaches for a card, and how long it pretends to think. Nothing at the tier level makes a robot blunder on purpose. That's the personality's job.

Depth is counted in half-moves, or plies. One ply is the robot's own move and nothing else. Two is its move and your reply. Three adds its next move; four adds your reply to that. The deeper tiers are capped at a few thousand positions a search, so a depth-four search usually finishes depth three and part of four. Card play is the share of its turns, with a card in hand, on which it looks for a card worth playing. It may still find nothing.

Beginner

One ply deep. It sees its own move and not your reply, so any one-move tactic lands. Six candidates. A card on about four turns in ten. It thinks for one and a half to four seconds, which is what comes off its clock.

• StupidFish (StupidFish, free): "The house robot. Finds a good move, then ignores it."
• PAWNBOT (Pawn Lover, free): "Pushes pawns. Only pawns, if it can help it."
• OOPS.BAT (Blunderer): "Every move is a surprise, mostly to itself."
• PIGGYBANK (Material Hoarder): "Saves every piece it's ever been given."
• SLOT-0 (Gambler): "Pulls the lever on every move."
• BLOOP (Chaos Goblin): "Moves pieces mostly to watch them move."
• Q-TIP (Queen Sacrificer): "Pokes its queen into everything."
• TRY-HARD 1.0 (Grandmaster): "Always plays its best move. Can only see one move ahead."

Novice

Two plies. It sees your reply now, so the free piece has to be two moves off. Six candidates. A card on half its turns. Two to five seconds a move.

• BLUNDR-1 (Blunderer, free): "Means well. Drops a piece most games."
• LOOT.EXE (Material Hoarder, free): "Grabs anything that isn't nailed down."
• MINNOW.EXE (StupidFish): "A very small StupidFish."
• PUSHR (Pawn Lover): "Back rank? Never heard of it."
• SCRATCHCARD (Gambler): "Thinks the next move might be the big one."
• STATIC (Chaos Goblin): "Fuzzy reception, fuzzier plans."
• QUEENSACK (Queen Sacrificer): "Bags its own queen and walks away."
• HOMEWORK.BOT (Grandmaster): "Did the reading. Skipped the practice."

Casual

Still two plies, but five candidates instead of six. A card on six turns in ten. Two and a half to six seconds a move.

• COINFLIP (Gambler, free): "Heads, it attacks. Tails, it also attacks."
• GL1TCH (Chaos Goblin, free): "Its moves make sense to someone, somewhere."
• GUPPY 2.0 (StupidFish): "Sees the right move. Prefers the funny one."
• P4WNSTORM (Pawn Lover): "Rolls a wall of pawns down the board."
• ERR0R 404 (Blunderer): "Its best move could not be found."
• H0ARD-3R (Material Hoarder): "Won't trade. Won't share. Won't let go."
• ROYAL.DEL (Queen Sacrificer): "Deletes its own queen to free up space."
• CLIPBOARD (Grandmaster): "Does everything by the book."

Intermediate

Three plies: its move, your reply, its next. The first tier that sees its own follow-up, so a threat it makes is usually real. Five candidates. A card on about seven turns in ten. Three to seven and a half seconds a move.

• SACBOT (Queen Sacrificer, free): "Hands you its queen and calls it strategy."
• TROUT.SYS (StupidFish): "Analyses deeply. Chooses poorly."
• PAWNSHOP (Pawn Lover): "Every piece is a pawn if you believe hard enough."
• CRASHTEST (Blunderer): "Solid, right up until impact."
• VAULT-7 (Material Hoarder): "Pieces go in. Pieces do not come out."
• D1CE (Gambler): "Picks the sharpest move on the board."
• SCRAMBLER (Chaos Goblin): "Mixes up its own plans, then yours."
• METRONOME (Grandmaster): "Steady and sensible, one move after another."

Advanced

Three plies with four candidates, so even the random personalities choose among decent moves. A card on more than eight turns in ten. Four to nine seconds a move.

• OVERCLOCK (Grandmaster, free): "Runs hot. Always plays its best move."
• BARRACUDA (StupidFish): "Has teeth. Sometimes bites itself."
• IRONCLAD (Pawn Lover): "An armoured column of pawns."
• BLUESCREEN (Blunderer): "Brilliant, until it suddenly isn't."
• DRAGON.DAT (Material Hoarder): "Sleeps on a pile of your pieces."
• HIGHROLLER (Gambler): "Bets big. Usually on itself."
• KERNEL PANIC (Chaos Goblin): "Plenty of power. One loose wire."
• Q-SAC 9000 (Queen Sacrificer): "Sees the whole board. Gives you the queen anyway."

Expert

Four plies, as far as any robot looks, with three candidates, which blunts the Chaos Goblin and sharpens the Gambler. A card on nine turns in ten. Five to eleven seconds a move.

• STUPIDFISH XL (StupidFish): "Deep analysis, deliberately wasted."
• PHALANX (Pawn Lover): "Pawns in perfect formation."
• HUBRIS.EXE (Blunderer): "Too good to lose. Loses anyway, sometimes."
• BANKBOT (Material Hoarder): "Collects interest on every piece it takes."
• JACKPOT (Gambler): "Plays for the knockout, every move."
• WILDCARD (Chaos Goblin): "Expert-level nonsense."
• REGICIDE.SYS (Queen Sacrificer): "Throws its queen like a grenade."
• SENTINEL (Grandmaster): "Never rushes. Never slips."

Grandmaster

Four plies, three candidates, a card on nineteen turns in twenty, and six to thirteen seconds a move. The only thing separating these eight is the personality, and that's the only flaw each one has.

• LEVIATHAN (StupidFish): "The biggest fish. Still stupid on purpose."
• COLOSSUS (Pawn Lover): "Eight pawns, one direction."
• ICARUS (Blunderer): "Flies close to perfect, then falls."
• FORT KNOX (Material Hoarder): "You will not get its pieces."
• HOUSE EDGE (Gambler): "The odds are always in its favour."
• SINGULARITY (Chaos Goblin): "Unknowable. Possibly broken."
• KINGMAKER (Queen Sacrificer): "Gives up the queen for the king's sake."
• MAINFRAME (Grandmaster): "No jokes. The final boss."

Which to play first

Eight robots are free for every account, climbing from Beginner to Advanced with a different personality at each step. The other forty-eight need the robots perk, which comes with a membership, and every new account has it for its first seven days as a free trial.

Start with StupidFish. Win a few. Then go straight to OVERCLOCK and lose a few, because the gap between a one-ply robot that ignores its best move and a three-ply robot that plays it every time is where you learn what the cards are for. When OVERCLOCK stops winning, the rest of the roster is waiting, and so is MAINFRAME. If you've never played a robot at all, your first robot game covers the setup.

Beating the free eight

StupidFish sees one ply and then plays its third or fourth choice. Make threats. It won't answer them.

PAWNBOT pushes pawns and leaves its pieces at home. Develop yours, then go through the holes the pawns left behind.

BLUNDR-1 plays a worse move about three times in ten, and at two plies a worse move is often a loose piece. Keep a sound position and wait. It comes.

LOOT.EXE takes what you leave out and won't move its queen. Hang a pawn where taking it costs a tempo, and attack a queen that never gets to leave.

COINFLIP plays the best or second-best move most of the time. Put it in positions where only one move holds, and it finds the wrong one two times in three.

GL1TCH picks among five moves at random. Any plan beats no plan. Let it wander.

SACBOT sees three plies, and will still trade its queen for a defended piece. Check what covers the square it just landed on. Then take the queen.

OVERCLOCK has no habit to exploit. It plays its best move three plies deep and a card most turns. Beat it with something outside its search: a Freeze on the defender it was counting on, a Bear Trap: e-file laid face down on the file it has to use, a Hall of Mirrors that makes the board do something its evaluation wasn't built around. And don't hand it tactics; three plies is enough to take anything you leave loose.

Beating all eight is the Starter Pack achievement. There's one for beating a robot at each difficulty, from Hello, World at Beginner to Giant Slayer at Grandmaster, plus Robot Wrangler for five different robots, Recycling Plant for twenty, and Scrap Metal for all fifty-six. Beating MAINFRAME is Final Boss. If you keep losing to the same robot in the same way, ten mistakes new players make is probably where the answer is.