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Reversi looks deceptively simple: a near-empty 8×8 board, two starter discs each, and a single move type. But the moment you outflank your first row, you discover the twist that makes this game brutal — every disc you own can be stolen back, and the player ahead at move 30 often loses at move 60. On Classic Play you place discs to bracket and flip your opponent's, fighting for the four unflippable corners while denying them yours. Black always moves first, and one careless square next to a corner can hand the whole game away.
How to Play Reversi
Reversi is played on an 8x8 board that starts with four discs locked in the centre: two white on one diagonal and two black on the other. Black always moves first. On your turn you place one disc on an empty square so that it traps at least one straight, unbroken line of your opponent's discs between the disc you just placed and another disc of your own colour. Lines can run horizontally, vertically, or diagonally, and a single placement can flip in several directions at once.
Every opponent disc caught between your two discs flips to your colour immediately. A move is only legal if it flips at least one disc, so you can never simply 'pass to a quiet square' — if you have any flipping move available, you must make one. If you have no legal move at all, your turn is skipped automatically and your opponent plays again. The game continues until neither player can move, which is usually but not always when all 64 squares are filled.
When neither side has a legal move, the discs are counted: whoever owns more discs wins, and an equal count is a draw. Against the computer you can choose Easy, Medium, or Hard, and an undo button lets you take moves back while you are learning the flipping patterns.
Reversi Strategy: Corners, Mobility, and the Disc-Count Trap
The single biggest mistake new players make is greed. Discs flip constantly, so being ahead on disc count in the opening and midgame means almost nothing — it often means you are losing. A bloated position gives you fewer empty squares to play into, which crushes your mobility (the number of legal moves you have). The strong plan is the opposite of instinct: flip as FEW discs as possible early, keep your pieces clustered near the centre, and force your opponent to run out of safe moves first. When they have no good move, they must play an edge or a corner-adjacent square and hand you a real, permanent gain.
Corners are the only squares that can never be flipped, and on Classic Play the Hard AI knows this — its evaluation scores a corner at +100 and the squares next to corners at -40. Treat that table as a warning. The four diagonal-to-corner squares (the X-squares, like b2 and g7) are the most dangerous in the game: occupying one almost always lets your opponent drop into the corner beside it on their next turn. The C-squares (the edge squares one step from a corner, like a2 or b1) are nearly as risky. Avoid all of them unless the neighbouring corner is already yours or provably safe.
Edges are powerful because edge discs can only be outflanked along the edge itself or diagonally inward, but they are a trap if you build them carelessly. Aim for stable discs — discs that can never be flipped because they are backed by your own pieces or the board edge in every direction. Stability radiates out from corners you already own, so a corner plus the edge filling outward from it becomes an untouchable anchor. Building an isolated wall in the middle of an edge, on the other hand, frequently gifts the adjacent corner to your opponent.
The endgame inverts everything. In the final ten to fifteen moves the game stops being about position and becomes pure arithmetic, because there is no longer time for discs to be flipped back — now you flip aggressively and cash the stable corners and edges you secured earlier into sweeping captures of entire rows. Watch parity: when only a few empty squares remain in a region, the player forced to move into that pocket first usually loses it. The opponents differ here too — Easy blunders randomly about four moves in ten and looks only two moves ahead, Medium blunders roughly one in ten, and Hard never blunders and searches five plies, weighing corner control, mobility, a positional square table, and a disc-count term that grows as the board fills, so beating Hard means genuinely managing mobility rather than grabbing discs.
Frequently Asked Questions
Who moves first in reversi, and does it matter?
Black always moves first here, matching standard Othello rules. The first move is a small disadvantage at the top level rather than an edge, because moving first uses up flexibility; in even games perfect play is believed to end in a draw, but among human players the difference is minor.
Can I pass my turn if I don't like any of my moves?
No. You may only pass when you have zero legal flipping moves, and the engine does that automatically by skipping you. If even one move that flips a disc exists, you are forced to play it, so you cannot deliberately sit out a turn.
Why is having more discs in the middle of the game often bad?
Because discs flip back and forth, an early lead is unstable and tends to shrink your mobility — owning more squares leaves you fewer empty cells to play into. Strong play means flipping few discs early to keep options open, then flipping aggressively only in the final ten to fifteen moves.
What are X-squares and C-squares, and why avoid them?
X-squares are the four squares diagonally next to a corner (like b2); C-squares are the edge squares one step from a corner (like a2). Playing either usually lets your opponent drop straight into the adjacent corner, which can never be flipped back, so avoid them unless that corner is already safely yours.
Does the game always end with the board full?
Not necessarily. The game ends as soon as neither player has a legal move, which can happen before all 64 squares are filled. Empty squares left at the end simply count for nobody — only the discs on the board are tallied, and the higher count wins.