Checkers

Checkers — how to play and tips

Checkers — English draughts — played against a computer opponent that actually searches ahead rather than moving at random. Move your pieces diagonally forward, jump over the AI's pieces to capture them, and try to take everything it has or leave it with no legal move at all, since either one ends the game in your favour.

How to play

Tap one of your pieces, then tap a highlighted square to move there. Green dots mark ordinary quiet moves and red dots mark captures, so you can see at a glance which destinations end the turn quietly and which take a piece off the board. Pieces that are currently able to move at all are ringed in green before you select anything, which matters a great deal once the compulsory-capture rule below kicks in — some turns only one single piece on the whole board is legally allowed to move, and the ring is what tells you which one. Undo takes back your entire last turn and the AI's reply to it together, restoring the board to exactly how it looked before you moved; on desktop, U or Ctrl+Z does the same thing as the on-screen Undo button. A New Game button resets the board to the starting position at any point without leaving the match screen.

Captures are compulsory

This is the rule casual versions most often get wrong. If any capture is available anywhere on the board — even for a piece you weren't planning to move — you must take one; a quiet move is simply illegal that turn and the game will never even offer it to you as an option. That's the actual reason why sometimes only a single piece lights up as movable: every other piece either has no legal quiet move or has one that the forced capture rule overrides. It cuts both ways, though, and that's part of the strategy: you can deliberately offer the AI a piece to force it into a capture it has no choice but to take, sometimes walking it straight into a worse position than it would otherwise have chosen.

Multi-jumps and crowning

If a piece can jump again immediately after landing from its first jump, it must keep jumping — the entire chain of captures counts as one single move, and you cannot stop partway through to switch to a different piece or decline the rest of the sequence. The one exception is promotion: a man that lands on the far row during a jump is immediately crowned a king and the turn ends right there, even if the newly landed piece could technically have jumped again. Kings move and capture in all four diagonal directions instead of only forward, which makes them far more dangerous and much harder to trap.

That crowning exception matters more than it sounds. Implementations that miss it let a piece get crowned mid-chain and then immediately continue jumping backwards on the very same turn it was promoted, which is a large and well-known unfair advantage in checkers — a freshly minted king should have to wait for its next turn to use its new backward reach, and that's exactly what happens here.

The AI

The computer opponent uses negamax search with alpha-beta pruning, and its board evaluation weighs material count, the extra value of kings over regular men, how far advanced each man is toward being crowned, whether your back row is still held to deny easy promotions, and whether pieces sit on the edge files, which can never be captured from the side. Crucially, the search explores complete jump sequences as single moves rather than scoring individual hops in isolation — scoring hops separately would let the AI's search stop partway through a forced chain and evaluate a board position that could never actually occur in a real game, since the rules require the whole chain to be played out.

Easy looks two moves ahead and, on top of that shallow search, plays a completely random legal move roughly a third of the time, which is what keeps it beatable even by a fairly new player. Medium searches four moves ahead and plays consistently rather than randomly. Hard searches six moves ahead, which is deep enough that it will actively set up multi-move traps — offering a piece now that leads to a forced double capture for it two or three moves later — rather than only reacting to whatever is on the board right now.

Tracking your results

Your win, loss and draw record is saved on your device and shown on the start screen before every game, along with the difficulty you last played, so you can see over time whether you're actually improving against a given level before stepping up to a harder one. A draw is recorded whenever neither side can force a win and the game reaches a position with no legal moves for the player to act — the same rule that ends the game outright applies to draws by exhaustion, not just to being fully captured.

Strategy

Hold your back row for as long as you reasonably can — those two squares are the only thing stopping the AI's men from reaching the crowning row uncontested, and the evaluation function above literally scores keeping them occupied. Play toward the edge files once you're ahead in material, since a piece sitting on the leftmost or rightmost column can never be captured from that side, cutting the AI's options against it in half. And remember that offering a piece is a real, usable weapon rather than always a blunder: because captures are forced, a deliberate sacrifice can drag the AI's piece to a square it would never have chosen to occupy on its own, setting up a double jump or a clean shot at a king in return.