Reversi
Play Reversi (Othello) against a positional AI. Flank and flip your opponent's disks to win.
About Reversi
Reversi has been played under various names since at least the 1880s in England, and its best-known branded version, Othello, turned it into a global phenomenon after its 1970s relaunch in Japan — but the underlying game, and its generic name, predates any trademark by nearly a century. The rules are compact: starting from four disks in the center of an 8×8 board, players alternate placing a disk of their color on any empty square that "flanks" one or more of the opponent's disks in a straight line — an unbroken row of the opponent's disks bordered by your own on both ends — and every flanked disk flips to your color.
What makes Reversi deceptively deep is that the disk count barely matters until the very end; a position with far fewer disks on the board can easily be winning if it controls the right squares, especially the four corners, which can never be flipped once claimed and often anchor an entire edge. Our AI opponent doesn't just count disks — it weighs corner and edge control heavily and factors in mobility (how many moves are available to each side), which mirrors how strong human players actually think about the position, rather than greedily grabbing the most disks available on any given turn. If neither player has a legal move on their turn, that player passes automatically and play continues; the game ends when neither side can move, and whoever holds the most disks at that point wins.
How to Play
- 1Tap an empty square that flanks one or more of the AI's disks in a straight line to place your disk there
- 2Every one of the opponent's disks caught between your new disk and another of your disks in that line flips to your color
- 3If you have no legal move, your turn is skipped automatically
- 4The game ends when neither player can move
- 5Whoever has the most disks on the board when the game ends wins
Tips & Strategy
- Prioritize the four corners above everything else — a disk placed in a corner can never be flipped, and corners often anchor control of an entire edge.
- Avoid placing disks in the squares diagonally next to a corner early on — they often hand the AI a free path to take that corner.
- Don't chase the highest disk count early in the game — having fewer disks on the board can actually limit your opponent's options and set up a stronger position later.
- Pay attention to mobility: a move that leaves you with more legal follow-up options than your opponent is often better than one that just flips the most disks.
- Edges are valuable but riskier than corners — control them, but watch for moves that let your opponent flip an entire edge back.
Frequently Asked Questions
What's the difference between Reversi and Othello?
They're the same core game. Reversi is the older, generic name dating to the 1880s; Othello is a specific branded version launched in Japan in the 1970s with a fixed starting position rule. This version uses the classic Reversi rules and name.
Why doesn't having more disks always mean I'm winning?
Board position matters more than disk count for most of the game, especially corner and edge control, since those disks are hard or impossible to flip. A big disk lead in the midgame can evaporate quickly if your opponent controls the right squares.
What happens if I have no legal move?
Your turn is automatically skipped and play passes to the opponent. If neither player can move, the game ends immediately and disks are counted.
How does the AI decide its moves?
It uses a minimax search that weighs corner and edge control alongside mobility (the number of moves available to each side), not just the number of disks it would flip on a given turn.
