Screen _NewImage(600, 600, 32)

CENTERX = 300

CENTERY = 300

' Pringle parameters

SIZE = 300

STP = 1

Const ZSCALE = 30 ' Controls how much "curve" there is

num = 20

dir = 20

t = 4



Do

    If num > 3000 Then

        dir = -20

    End If

    If num < -3000 Then

        dir = 20

    End If

    num = num + dir * t

    For x! = -SIZE To SIZE Step STP

        For y! = -SIZE To SIZE Step STP

            ' Hyperbolic paraboloid formula: z = (x^2 - y^2) / scale

            z! = ((x! ^ 2) - (y! ^ 2)) / (SIZE * ZSCALE)



            ' Project to screen (top-down view with z as shading)

            screenX = CENTERX + x!

            screenY = CENTERY + y!



            ' Shade based on height (z)

            shade = 128 + z! * num

            If shade < 0 Then shade = 0

            If shade > 255 Then shade = 255



            PSet (screenX, screenY), _RGB(shade, shade, 255 - shade)

        Next

    Next

Loop Until InKey$ = Chr$(27)