Graphics 800,600,16,2
SetBuffer BackBuffer()

Function Twirl(X, Y, R, A#, B=0)
   If B=0 B = BackBuffer()
   IMG = CreateImage(R*2+2,R*2+2) : IB = ImageBuffer(IMG) : CopyRect X-R-1,Y-R-1,R*2+2,R*2+2,0,0,B,IB
   Red = ColorRed() : Gre = ColorGreen() : Blu = ColorBlue() : RGB = Red * $10000 + Gre * $100 + Blu
   LockBuffer B : LockBuffer IB
   For R1 = 1 To R
      VA# = 25.0/R1 : D# = 0
      While D# < 360
         D# = D# + VA# : De# = D# + A#*VA#
         C1# = X+Cos(D#) *R1 : S1# = Y+Sin(D#) *R1 : C2# = R+Cos(De#)*R1 : S2# = R+Sin(De#)*R1
         RGB2 = ReadPixelFast(C1#, S1#, B)
         WritePixelFast(C2#, S2#, RGB2, IB)
      Wend
      LD = LD + 1
   Next
   UnlockBuffer B : UnlockBuffer IB
   DrawBlock IMG,X-R-1,Y-R-1 : FreeImage IMG
End Function

img2 = CreateImage(400,400)
SetBuffer ImageBuffer(img2)
For A = 0 To 200
   Color A,A,A
   Rect A,A,400-A*2,400-A*2,0
Next
SetBuffer BackBuffer()
A = -100
While Not KeyHit(1)
   Cls
   DrawImage img2,200,100
   
   msec = MilliSecs()
   Twirl(MouseX(),MouseY(),100,A)
   msec = MilliSecs() - msec
   Text 0,0, msec
   If MouseDown(1) A = A + 10
   If MouseDown(2) A = A - 10
   
   Flip
Wend

Graphics 800,600,0,2
SetBuffer FrontBuffer()

radius#=200
xp=250
yp=250

For x#=0 To radius Step 1
   wt%=Sin(ACos(x/radius))*radius
   Rect xp+x,yp-wt,1,wt*2,1
   Rect xp-x,yp-wt,1,wt*2,1
Next

WaitKey