Paint curves

\[Theta]step = Pi/2;
nmax = 3;
point[r_, \[Theta]_] :=
  With[{\[Theta]t = Mod[\[Theta], \[Theta]step, -\[Theta]step/2],
    n = Floor[\[Theta]/\[Theta]step + 1/2]},
   2 r {Cos[\[Theta]t] (-1)^n,
      Sin[-\[Theta]t]} - {(-1)^(n) Cos[\[Theta]step/2],
     2 n Sin[\[Theta]step/2]}
   ];
frame[\[Theta]max_] := (Show[
    Join[{
      Graphics[{
        EdgeForm[], FaceForm[RGBColor[0.0, 0.3, 0.9]],
        Rectangle[{-Cos[\[Theta]step/2], -2 nmax Sin[\[Theta]step/
             2]}, {Cos[\[Theta]step/2], 0}]
        },
       PlotRange -> {
         1.5 {-1, 1}, {0.1, -2 nmax Sin[\[Theta]step/2] - 0.1}}
       ]
      },
     Table[
      ParametricPlot[
       point[r, \[Theta]]
       , {\[Theta], 0, \[Theta]max},
       PlotStyle ->
        Lighter@ColorData["RedBlueTones"][1 - 4 r (1 - r)],
       Exclusions -> Mod[\[Theta], \[Theta]step] == \[Theta]step/2,
       Axes -> None],
      {r, 0, 1, 1/30}
      ],
     {Graphics[{
        {FaceForm[White], EdgeForm[],
         Rectangle[{-1.5,
           0}, {-Cos[\[Theta]step/2], -2 nmax Sin[\[Theta]step/2]}],
         Rectangle[{Cos[\[Theta]step/
             2], -2 nmax Sin[\[Theta]step/2]}, {1.5, 0}]},
        {Thick, Darker@Red,
         Line[
          Table[
           point[r, \[Theta]max],
           {r, 0, 1, 1/30}
           ]
          ]
         }
        }
       ]}
     ]]);
Manipulate[
 frame[\[Theta]max],
 {\[Theta]max, 0.01, \[Theta]step nmax}
 ]