Use APP_PORT consistently

README.md

@@ -13,6 +13,8 @@ A notepad-playable browser game that combines Tic Tac Toe's line-making goal wit
 
 ## Run With Docker Compose
 
+Optional: copy `.env.example` to `.env` and change `APP_PORT`.
+
 ```powershell
 docker compose up --build
 ```
@@ -37,12 +39,12 @@ docker compose down
 npm start
 ```
 
-Then open `http://localhost:3000` in two browser windows.
+Then open `http://localhost:8787` in two browser windows.
 
 Set a different port with:
 
 ```powershell
-$env:PORT=4000; npm start
+$env:APP_PORT=9090; npm start
 ```
 
 ## Notes