Osero (also called Othello or Reversi) is a strategy game for two players on an 8×8 board.

🎯 Goal

Have the most discs of your color when the game ends.

⚙️ Rules

• Black always goes first.
• To place a disc, you must sandwich at least one opponent disc between your new disc and another of your own — in a straight line (horizontal, vertical, or diagonal).
• All sandwiched discs in every valid direction flip to your color at once.
• A move is only legal if it flips at least one disc.
• If you have no legal moves, your turn is skipped — you don't lose!
• If neither player can move, the game ends immediately.
• The game also ends when the board is full.

🏆 Winning

The player with the most discs wins. Equal count = draw.

💡 Pro Tip

Corners are king. A disc in a corner can never be flipped. Never give one up — and always try to take one.