Why Mistakes Matter More Than Brilliance

In reversi, you don’t need brilliant moves to win. You need to stop making bad ones. The difference between a beginner and an intermediate player isn’t that the intermediate finds amazing plays — it’s that they’ve stopped throwing away positions with avoidable errors.

Here are the 12 most common mistakes, ranked roughly from most damaging to least, with concrete fixes for each.

Mistake #1: Maximizing Disc Count

The error: Flipping as many discs as possible every turn.

Why it’s wrong: This is the single most destructive habit in reversi. Every disc you flip becomes part of your frontier — exposed to the opponent on future turns. Maximizing discs means maximizing your frontier, which means minimizing your mobility. By the midgame, you’ll have dozens of discs but only 1–2 legal moves, while your opponent controls the board.

The fix: In the early and midgame, prefer moves that flip one disc rather than four. Choose quiet moves that keep your position compact. Think of discs as liabilities, not assets — at least until the endgame.

Remember: Only the final disc count matters. Having 40 discs on move 30 means nothing if you end with 25.

Mistake #2: Playing on X-Squares

The error: Moving to b2, b7, g2, or g7 when the adjacent corner is empty.

Why it’s wrong: X-squares are the most dangerous positions on the board. Playing on an X-square gives your opponent access to the adjacent corner on their very next move. Corners are permanent, unflippable anchors — giving one away for free is often game-losing.

The fix: Treat X-squares as forbidden territory unless the adjacent corner is already taken. Before every move, check: “Am I about to play on an X-square?” If yes, find literally any other move.

Exception: If you already own the adjacent corner, the X-square becomes perfectly safe and often strategically valuable as part of a stable disc formation.

Mistake #3: Careless C-Square Play

The error: Playing on C-squares (the squares adjacent to corners along the edge) without considering the consequences.

Why it’s wrong: C-squares are less immediately dangerous than X-squares, but they can still lose corners. A C-square play often gives the opponent an angle to attack the adjacent corner, especially when combined with edge control.

The fix: Before playing a C-square, ask: “Can my opponent reach the corner now?” Check whether your C-square play creates a sequence the opponent can exploit. In the opening and midgame, avoiding C-squares is usually the right default.

Mistake #4: Ignoring Mobility

The error: Making moves without considering how many legal moves you’ll have next turn or how many your opponent will have.

Why it’s wrong: Mobility is the most important strategic concept in reversi. A player with 10 legal moves has 10 options; a player with 2 has almost no flexibility. Low mobility means you’re being forced into bad positions, and eventually you’ll be forced onto an X-square or into giving away a corner.

The fix: Before each move, count your legal moves and your opponent’s legal moves (or at least estimate). Choose moves that keep your options open and reduce your opponent’s choices. Prefer moves that flip interior discs rather than exterior ones.

Mistake #5: Rushing to the Edges

The error: Playing on edge squares in the opening or early midgame because they “look safe.”

Why it’s wrong: Edges feel stable, but early edge play is often disastrous. An unbalanced edge (one where you hold several consecutive edge squares with your opponent on one side) can be attacked with a wedge — a move that splits your edge and allows the opponent to eventually take a corner.

The fix: Stay in the center for as long as possible. Edges become valuable in the midgame and endgame when you can create balanced edges or connect edge discs to corners. In the opening, edge moves usually just create vulnerabilities.

Mistake #6: Not Recognizing the Stoner Trap

The error: Walking into Stoner traps — edge sequences where the opponent forces you to give up a corner.

Why it’s wrong: The Stoner trap is the most common tactical pattern in reversi. It works like this: your opponent occupies one end of an edge with a gap, then fills the edge forcing you to play the square adjacent to a corner (a C-square), which then lets them take the corner.

The fix: Study the edge strategy guide to recognize the Stoner pattern. Before extending along an edge, ask: “Is my opponent setting up a trap at the end of this edge?” If you see a gap in the edge with your opponent positioned behind it, stop extending.

Mistake #7: Forgetting About Parity

The error: Not tracking who plays the last move in each region of the board.

Why it’s wrong: Parity determines who gets the last move — and the last move in a region is almost always advantageous. If you’re ignoring parity, you’re essentially giving your opponent free advantageous moves throughout the endgame.

The fix: In the endgame (roughly the last 15–20 moves), start counting empty squares in each region. Odd-count regions favor the active player; even-count regions favor the responding player. Make move choices that give you the last play in as many regions as possible.

Mistake #8: Panicking When Behind on Disc Count

The error: Changing strategy because you have fewer discs on the board.

Why it’s wrong: Having fewer discs in the midgame is often a good sign. It means your position is compact, your frontier is small, and your mobility is likely high. Many winning games involve being behind 10–50 on discs for most of the game and then flipping massive groups in the last 10 moves.

The fix: Ignore disc count until the endgame. Judge your position by mobility (how many legal moves you have), stability (how many discs can never be flipped), and corner control. If you have good mobility and a corner or two, you’re probably winning — even if the board looks “bad” by disc count.

The error: Seeing a legal move and immediately playing it because it looks reasonable.

Why it’s wrong: Reversi is a game where obvious-looking moves are often terrible. A move that flips discs on the edge “feels” productive but might be exactly what your opponent wants — it could extend their stable disc formation or set up a Stoner trap.

The fix: Before every move, consider at least your top 2–3 options. For each, ask: “What will my opponent do after this?” Even 10 seconds of analysis per move dramatically improves play.

Mistake #10: Misjudging the Endgame Transition

The error: Continuing to play a midgame mobility strategy when the game has shifted to the endgame.

Why it’s wrong: Reversi has a critical transition point, usually around 15–20 empty squares remaining. Before this point, mobility strategy dominates. After it, disc counting and parity take over. Players who fail to switch strategies often waste their good midgame positions by making inefficient endgame moves.

The fix: Practice recognizing the transition. When about 20 empty squares remain, shift your focus from “how many moves do I have?” to “who plays last in each region?” and “how many net discs does each move gain?”

Mistake #11: Overvaluing Temporary Position

The error: Feeling comfortable because you control a large area of the board.

Why it’s wrong: In reversi, positions flip constantly. Controlling 50 out of 64 squares on move 50 means nothing if those discs all get flipped in the final 14 moves. Unlike chess where material advantage is permanent, reversi discs are always vulnerable unless they’re stable.

The fix: Evaluate your position by counting stable discs (discs that can never be flipped) rather than total discs. A player with 10 stable discs in a corner formation is in a much better position than a player with 40 unstable discs spread across the board.

Mistake #12: Not Studying the Board Before Moving

The error: Moving quickly without scanning the entire board for opportunities and threats.

Why it’s wrong: Reversi’s 8×8 board is small enough that you can — and should — scan every legal move before choosing. Unlike larger games, you can realistically evaluate all options. Players who don’t scan miss tactical shots, Stoner traps, forced sequences, and corner opportunities.

The fix: Before every move, scan the entire board. Check all four corners: is one available? Check all X-squares and C-squares: is your opponent about to give one away? Check edges: is a wedge available? Only after scanning should you choose your move.

A Quick Self-Diagnostic

Ask yourself these questions after your next game:

  1. Did I ever flip more than 3 discs when a 1-disc flip was available?
  2. Did I play on an X-square when the corner was empty?
  3. Did I rush to an edge before move 15?
  4. Did I panic about disc count?
  5. Did I consciously track parity in the endgame?

If you answered “yes” to #1–4 or “no” to #5, you found your next improvement area. Fix one mistake at a time, starting with whichever costs you the most games. Most players see dramatic improvement just by fixing mistakes #1 and #2.