Plot filled spiral.

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Sub Test_Plt_Fill()
    Const A = 1, B = 0.2
    Dim Theta() As Double, X1() As Double, Y1() As Double, X2() As Double, Y2() As Double
    Dim D As Double, N As Long, I As Long, J As Long
    Dim K As Long
    N = 0: D = 0
    While D < 8 * Pi()
        D = D + 0.1
        N = N + 1
    Wend
    ReDim Theta(N), X1(2 * N), Y1(2 * N), X2(N), Y2(N)
    For I = 0 To N - 1
        Theta(I) = I * 0.1
    Next
    D = 0: K = 0
    While D < 2 * Pi()
        For I = 0 To N - 1
            X1(I) = A * Cos(Theta(I) + D) * Exp(B * Theta(I))
            Y1(I) = A * Sin(Theta(I) + D) * Exp(B * Theta(I))
            X2(I) = A * Cos(Theta(I) + D + Pi() / 4) * Exp(B * Theta(I))
            Y2(I) = A * Sin(Theta(I) + D + Pi() / 4) * Exp(B * Theta(I))
        Next
        For I = 0 To N - 1
            J = N - I - 1
            X1(N + I) = X2(J)
            Y1(N + I) = Y2(J)
        Next
        Call Plt.Fill(2 * N, X1(), Y1())
        D = D + Pi() / 2: K = K + 1
    Wend
    Call Plt.Show
End Sub