The Disc Count Paradox

Before learning any specific tactic, you need to understand reversi’s most counterintuitive principle: having fewer discs is often better than having more during the opening and midgame.

This shocks beginners because every other board game rewards accumulating pieces. In chess, more pieces means more power. In checkers, capturing is mandatory. But in reversi, a player with 5 discs on the board can be in a vastly stronger position than a player with 20.

Why? Because disc count determines your frontier — the number of your discs with empty squares next to them. A large frontier gives your opponent many legal moves (places to outflank you). A small frontier constrains their options. When your opponent runs out of good moves, they’re forced into bad ones — like giving you corners.

This principle underlies everything below. Every tip connects back to it.

Tip 1: Corners Are the Most Important Squares

The four corner squares (a1, a8, h1, h8) are permanently stable — once a disc is placed there, it can never be flipped. No opponent disc can be placed beyond a corner to outflank it.

But corners do more than just survive. They anchor entire edges: once you own a corner, every disc you place along the connected edge becomes progressively harder to flip. A player who takes two corners on the same edge can often build a wall of 8 stable discs that are immune for the rest of the game.

Practical rule: Always take a corner when it’s available. If you must choose between a corner and any other move — take the corner. There are rare exceptions at advanced levels, but as a beginner, treat corners as the highest-priority targets on the board.

For a comprehensive breakdown, see the corner strategy guide.

Tip 2: Avoid X-Squares at All Costs

The X-squares — b2, b7, g2, g7 — are the four squares diagonally adjacent to corners. Playing on an X-square is one of the worst mistakes in reversi because it almost always lets your opponent take the adjacent corner on their next turn.

Here’s why: if you place a disc on b2, your opponent can place on a1 (the corner), using your b2 disc as the disc to outflank. You’ve essentially handed them a permanent, stable corner for free.

Practical rule: In the opening and midgame, treat X-squares as off-limits. The only time they become acceptable is in the late endgame when the adjacent corner is already taken, or when you’re forced to play there because all other moves are worse.

Tip 3: Be Cautious with C-Squares

C-squares are the squares directly adjacent to corners along the edges (a2, b1, g1, h2, a7, b8, g8, h7). They’re less dangerous than X-squares but still risky — playing a C-square can give your opponent a path to the corner, especially if the adjacent X-square is also occupied.

Practical rule: C-squares are not automatically terrible, but treat them with caution in the first half of the game. If you must play one, prefer C-squares where the adjacent X-square and corner are both empty — the risk is lower.

Tip 4: Maximize Your Mobility

Mobility — the number of legal moves available to you — is the most important positional concept in reversi after corners. High mobility means you have choices. Low mobility means you may be forced into moves that give up corners or create bad positions.

How to increase your mobility:

  • Flip fewer discs per move. Moves that flip 1–2 discs (called “quiet moves”) keep your frontier small.
  • Play toward the center. Central discs tend to have fewer empty squares adjacent to them, making them interior discs rather than frontier discs.
  • Don’t spread to the edges too early. Edge discs are exposed on the outside, expanding your frontier.

How to decrease your opponent’s mobility:

  • Surround their discs. When their discs are surrounded by yours, they have fewer places to make legal outflanks.
  • Force them into one region. If your opponent’s discs are clumped in one area, their legal moves are limited to that zone.

Tip 5: Play Quiet Moves in the Opening

A quiet move is one that flips very few discs — ideally just one. Quiet moves are powerful because they:

  1. Keep your disc count low (maintaining the paradox advantage)
  2. Minimize your frontier (reducing opponent outflanking opportunities)
  3. Preserve your mobility for later turns

The opposite — “noisy moves” that flip 5+ discs in multiple directions — looks impressive but usually destroys your position. You’ll end up with discs scattered across the board, a massive frontier, and an opponent with unlimited options.

Practical rule: In the first 20 moves, if you have a choice between flipping 1 disc and flipping 5 discs, the 1-disc move is almost always better unless the 5-disc move gets you a corner.

Tip 6: Don’t Rush to the Edges

Beginners often think edges are great because they look safe — there’s nothing behind them. But edge discs are actually a mixed bag:

Edge risks:

  • They expand your frontier (the outer side is always adjacent to empty squares until the edge fills up)
  • They can create unbalanced edge formations that your opponent exploits
  • Going to the edge early gives your opponent more legal moves in the center where positional control matters

When edges are good:

  • After you own the adjacent corner — then edge discs become stable
  • In the endgame when filling in the remaining squares
  • When a wedge play splits your opponent’s edge wall

Practical rule: Prefer center play in the opening. Move to edges when you have corner support or when the center is filled.

Tip 7: Think About Your Opponent’s Options, Not Just Your Score

After each potential move, ask yourself: “What can my opponent do after this?” This is more important than “How many discs did I flip?”

If your move leaves your opponent with 12 legal moves including corner access, it’s a bad move regardless of how many discs you flipped. If your move leaves your opponent with 3 legal moves — all of which are on terrible squares — it’s a great move even if you only flipped one disc.

This is the essence of positional thinking — evaluating a position based on what it allows rather than what it contains.

Tip 8: Control the Center Early

The center of the board (roughly the 4×4 block from c3 to f6) is the safest and most strategic area in the opening. Discs placed in the center tend to be:

  • Interior discs — surrounded by other discs, not touching empty squares
  • Low-frontier — contributing less to your opponent’s mobility
  • Flexible — providing outflanking lines in multiple directions for future moves

Practical rule: For the first 10–15 moves, keep your discs as close to the center as possible. Expanding outward should be driven by tactical necessity (like preventing your opponent from completing a dangerous formation), not by a desire to “claim territory.”

Tip 9: Watch for Forced Moves

A forced move is a position where your opponent has only one or two legal moves. This is extremely powerful because:

  1. You know exactly what they’ll play (eliminating uncertainty)
  2. Their forced move might be on a bad square (like an X-square or C-square)
  3. You can plan your next 2–3 moves in advance

The best position in reversi is one where you have many options and your opponent has few. Every move you make should ideally increase this asymmetry.

Tip 10: Don’t Panic When You’re “Losing” on Discs

During the midgame, you will frequently have fewer discs than your opponent. This is not losing — it might actually be winning. Remember the disc count paradox: fewer discs often means a smaller frontier, higher mobility, and positional superiority.

The only time disc count matters is at the very end of the game. A player with 10 discs can easily overtake a player with 30 discs in the final 15 moves if they have good position and parity control.

Practical rule: Ignore the disc counter during the first 40 moves. Focus entirely on mobility, corner control, and position. Disc count only matters in the last 15–20 moves — and by then, good position automatically translates into more discs.

Putting It All Together

Here’s how these tips work in a real game flow:

  1. Opening (moves 1–15): Play quiet moves in the center, keeping your disc count low and frontier small. Avoid edges, X-squares, and C-squares. Build interior discs.

  2. Midgame (moves 16–45): Maximize mobility by limiting your opponent’s legal moves. Maneuver to create corner opportunities. Force your opponent toward X-squares through positional pressure. When a corner becomes available, take it.

  3. Endgame (moves 46–60): Switch focus from mobility to disc maximization. Use parity to ensure you play last in key regions. Convert your positional advantage into final disc count.

The transition from midgame to endgame is the hardest part to learn. You’ll develop a feel for it over time. For now, just focus on the three biggest wins: take corners, avoid X-squares, and flip fewer discs.

What to Learn Next

Once these 10 principles are second nature, you’re ready for deeper strategy:

  • Corner strategy — when corners should be sacrificed and advanced corner techniques
  • Mobility strategy — the mathematics of frontier discs and move limitation
  • Edge strategy — wedges, Stoner traps, and unbalanced edges
  • Endgame strategy — parity, region counting, and the disc-maximization switch
  • Common mistakes — the 12 most frequent errors and how to fix them
  • Openings — named opening sequences used in competitive play