Only allow moves if there is no winner

src/js/Game.js

@@ -257,12 +257,15 @@ export class Game
      */
     addChip(x, y)
     {
-        for (let i = Game.#height - 1; i >= 0; i--)
+        if (!this.winner)
         {
-            if (this.board[i][x] === "")
+            for (let i = Game.#height - 1; i >= 0; i--)
             {
-                this.board[i][x] = this.state.currentPlayer;
+                if (this.board[i][x] === "")
-                return true;
+                {
+                    this.board[i][x] = this.state.currentPlayer;
+                    return true;
+                }
             }
         }