dim as integer X,Y,PX,PY,TX,TY,MTX,MTY
dim as double DX,DY
TX = 640:TY = 480
screenres TX,TY,32

MTX = TX shr 1:MTY = TY shr 1
DX = TX/255:DY = TY/255

for Y = 0 to TY
   for X = 0 to TX
     PX = X-MTX
     PY = Y-MTY
     pset(X,Y),rgb(255-(X/DX),(Y/DY),sqr((PX*PX)+(PY*PY))/DX)     
   next X
next Y

sleep