SOS looks like tic tac toe's slightly odd cousin: same pencil-and-paper feel, same grid, letters instead of noughts and crosses. Don't be fooled. Because you choose which letter to place every turn, and because completing an S-O-S earns you another turn, SOS has real strategic depth — and most casual players give away points on almost every move. Here's how to stop.
A quick refresher on how scoring works
On your turn you place either an S or an O on any empty square. Complete the sequence S-O-S in any direction — horizontally, vertically, or diagonally — and you score a point and move again immediately. The board fills up completely; whoever has more SOS points at the end wins. Both letters are always available to both players — that's the twist that makes everything interesting.
Rule one: learn what a dangerous square looks like
Most points in SOS aren't cleverly earned — they're donated. A move is dangerous if it creates a pattern your opponent can finish:
- S _ S with the gap empty — anyone can drop an O in the middle and score.
- S O _ or _ O S — an S on the open end scores.
Before every move, scan the three or four lines your square participates in — across, down, and both diagonals. Ask one question: after my letter lands, can any single letter placed by my opponent complete S-O-S through this square? If yes, that move is a gift. Early in the game there are plenty of safe squares, so there's no excuse for gifts.
Rule two: the extra turn is the whole game
Scoring one point is nice. But because a completed SOS grants another move, points come in chains: a good position lets you score, then score again with the bonus move, then again. Three points in a single visit to the board is a knockout blow in a close game.
To build chains, look for moves that create two scoring opportunities at once — for example, an O that sits between two S's on one line while also extending an S-O pair on another. Your opponent can only defuse one. This is SOS's version of the tic tac toe fork, and it's the main way strong players pull ahead.
Rule three: when no safe move exists, count
Sooner or later the board tightens and every move gives something away. This is where games are won. Don't just play the least-bad-looking square — count:
- How many points does each candidate move hand your opponent, including their chain moves?
- After their scoring spree ends, what does the board look like for you?
Sometimes the right play is a deliberate small sacrifice: give up a single point in a corner to avoid opening a three-point chain in the middle. Casual players never sacrifice; consistent winners do it every game.
Use the letters unequally
An easy habit that pays off: S is the aggressive letter, O is the safe one — roughly. An O in an empty area can never immediately create an S-O-S threat by itself, which makes O useful for waiting moves. An S placed near another S starts building potential in two directions at once. When in doubt on a crowded board, a lone O in a quiet corner is often the least generous move available.
Board size changes the tempo
On RivalPit you can play SOS from 4×4 up to 8×8. Small boards are knife fights — the unsafe phase arrives within a few moves, so counting skills dominate. Big boards reward patience: there's room to develop two or three scoring areas and force your opponent to defend everywhere at once. If you're the stronger tactician, pick the small board; if you like building, go big.
The five-second checklist
- Can I score right now? (Check every line — people miss diagonals constantly.)
- If I score, does my bonus move score again?
- Does my move let them score? Check all four directions.
- No safe move? Count the damage and pick the cheapest.
- Late game: track who takes the last turn — forced moves land on someone.