fix for undo state becoming corrupted after redo

js/pacosako.js

@@ -1129,7 +1129,7 @@ class Game {
          const savedRedo = this._redo;
 
          /* copy all the properties from the saved prior game to this one */
-         Object.assign(this, this._undo);
+         Object.assign(this, new Game(this._undo));
 
          /* restore the original redo history and add the undone move */
          this._redo = savedRedo;