I’m trying to build a tic tac toe program using a 3×3 board list running inside of a DynamicModule with a separate window displaying the current value and accepting clicks from the user. For now I’m just trying to use EventHandler to set any empty boxes to X‘s when clicked.

When I click on a box, I get the error “Part::pkspec1: The expression x cannot be used as a part specification.” (also for y). Is this an issue with assigning a new value for board inside of the EventHandler? How else should I structure this?

createBox[elem_] := Show[   Graphics[{White, Rectangle[]}, Frame -> True,     FrameStyle -> Thickness[.02], FrameTicks -> None],   Graphics@Text[Style[elem, FontSize -> 100], {.5, .5}],   ImageSize -> 150   ]    DynamicModule[{board = Table[Table[" ", 3], 3]},   CreateWindow[    DocumentNotebook[     (*Displaying grid*)     Dynamic@Grid[       Table[Table[         EventHandler[          createBox[board[[y]][[x]]]          , {"MouseClicked" :> (             If[board[[y]][[x]] == " ", board[[y]][[x]] = "X";];             )}]         , {x, 3}], {y, 3}],       Spacings -> {0, 0}]     ],    WindowElements -> {}, WindowTitle -> "Tic Tac Toe",     WindowSize -> All, Editable -> False, Selectable -> False,     ShowCellBracket -> False, WindowFrameElements -> {"CloseBox"}];   ];