Rotating Square Illusion

colors = ColorData["DarkRainbow"] /@ RandomReal[{0, 1}, 10];
Manipulate[
 Show[Reverse@
   Table[RegionPlot[((xt^4 + yt^4) /. {xt ->
          x Cos[\[Theta]] - y Sin[\[Theta]],
         yt -> y Cos[\[Theta]] + x Sin[\[Theta]]}) < r^4, {x, -2,
      2}, {y, -2, 2}, Frame -> None, PlotStyle -> colors[[10 r]],
     PlotRange -> Sqrt[2]], {r, 0, 1, 0.1}]
  ],

 {\[Theta], 0, 2 Pi}]