Prophylaxis (Preventing Their Plan): chess middlegame concept

Spot their idea, shut it down before it starts

Ask what the opponent wants, then take it away. The move that looks like nothing decides the game twenty moves later.

• Work out what the opponent threatens before choosing your move.
• A prophylactic move takes a square, a break, or a trade off the table.
• Good prophylaxis looks slow, which is why weaker players miss it.
• In doubt: improve your worst piece, deny their best move.