How to Play
Four discs start in the middle, two black and two white. Black always moves first: choose Play Black to start, or Play White to let the computer open. On your turn, place a disc on an empty square so that one or more straight lines of the computer's discs are trapped between your new disc and another of yours. Every trapped disc flips to your color.
With Show moves switched on, the squares where you can play are marked with a small dot. Tap or click one to place your disc and watch the line turn over. The computer then answers. The disc counts at the top show who is ahead, and the game ends when neither side can move.
Rules
- A move must flip at least one disc; a square that traps nothing isn't a move.
- Lines count across, down and diagonally, and every trapped line flips at once.
- A side with no legal move passes, and the other side plays again. This happens on its own.
- When neither side can move, usually because the board is full, the side with more discs wins. Equal counts are a draw.
- You get three undos a game. Each one takes back your last move and the computer's reply.
Tips & Strategy
Corners are forever
A disc in a corner can never be flipped, and it anchors the edges next to it. Avoid the squares touching an empty corner, because they usually hand the corner to your opponent.
Fewer discs, more choices
Grabbing lots of discs early often backfires. Keep your own moves open and leave the computer with few good ones; the count only matters at the very end.
Play quiet moves
Flipping one or two inside discs gives little away. Flipping long lines toward the edges opens squares for the other side.
FAQ
How strong is each level?
Easy usually grabs the move that flips the most discs and sometimes plays at random. Medium looks three moves ahead and knows which squares are valuable. Hard looks six moves ahead, weighs mobility, corners and safe edge discs, and searches the last ten empty squares through to the end.
What happens when I have no move?
You pass automatically and the computer moves again; a message tells you when it happens. The same applies to the computer, so you can sometimes play several moves in a row.
Why is undo limited?
Three undos a game take back a slip without letting you test every move against the computer's answer.
Is there a leaderboard?
No, Reversi is just for fun. Your games, wins, losses, draws, streak and biggest win are kept on this device for each level. Hard Checkers has a leaderboard if you want a ranked board game.