Add simple WebSocket multiplayer

README.md

@@ -11,9 +11,23 @@ A notepad-playable browser game that combines Tic Tac Toe's line-making goal wit
 - First player to make `4 in a row` wins.
 - If the board fills with no winner, the game is a draw.
 
-## Run
+## Run Multiplayer
 
-Open `index.html` in a browser.
+```powershell
+npm start
+```
 
-No build step is required.
+Then open `http://localhost:3000` in two browser windows. The first two connected players are paired automatically.
 
+Set a different port with:
+
+```powershell
+$env:PORT=4000; npm start
+```
+
+## Notes
+
+- No authentication or user accounts are required.
+- The server keeps games in memory only.
+- If an opponent closes their window, the remaining player sees a disconnect error and waits for a new player.
+- No build step is required.