txt = {"Ma", "the", "ma", "ti", "ca"};
pos = {0, 2.5, 4.85, 6.5, 7.95};
Clear[g]
Show[
        g = Graphics[{{GrayLevel[1], Point[{-1, 0}]}, {GrayLevel[1], 
                Point[{13, 0}]}}, 
            TextStyle -> {FontFamily -> "Times", 
                FontSize -> 36}, 
            AspectRatio -> 0.25]];
For[y = 1, 
      y ≤ Length[txt], 
For[x = 1, 
        x ≥ 0, 
g = 
          Show[{g, 
              Graphics[{{GrayLevel[x], 
                    Text[txt[[y]], {pos[[y]], 
                        0}  ]}, {GrayLevel[1], 
                    Point[{13, 0}]}}]}]; x = x - 0.1]; 
y = 
        y + 1;
]

Cell[
        BoxData[ButtonBox["Press here for fun", 
            ButtonFunction :> 
              FrontEndExecute[ {FrontEnd`SelectionMove[ButtonNotebook[ ], 
                    All, ButtonCell], 
                  FrontEnd`SelectionMove[ButtonNotebook[ ], Previous, Cell], 
                  FrontEnd`SelectionMove[ButtonNotebook[ ], Previous, Cell], 
                  FrontEnd`SelectionMove[ButtonNotebook[ ], All, CellGroup], 
                  FrontEnd`SelectionAnimate[ButtonNotebook[ ], 6.3]}], 
            Active -> True]]] // DisplayForm