' TassyJim
' 4th September 2015
' from a program in PureBasic by 'Idle' on the PureBasic forum.
'
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
OPTION EXPLICIT

DIM NumCircles = 5, Width = 240, Height = 200, pix = 2
DIM re
DIM mc(NumCircles,6)
main:
CLS
DO
re = initialise(NumCircles)
re = draw(NumCircles,pix)
LOOP
END

FUNCTION initialise(NumCircles)
LOCAL i
FOR i = 0 TO NumCircles
mc(i,1) = RRandom(0, Width) 'x
mc(i,2) = RRandom(0, Height) 'y
mc(i,3) = RRandom(20, 80) 'd
mc(i,4) = mc(i,3)/ 2 'r
mc(i,5) = RRandom(-3, 3) 'vx
mc(i,6) = RRandom(-3, 3) 'vy
NEXT i
END FUNCTION

FUNCTION draw(NumCircles,sx)
LOCAL x, y, dx, dy, sum, dd, i
FOR i = 0 TO NumCircles 'move circles AND keep in bounds
mc(i,1) = mc(i,1) + mc(i,5)
mc(i,2) = mc(i,2) + mc(i,6)
IF mc(i,1) - mc(i,4) <= 0 THEN
mc(i,5) = ABS(mc(i,5))
ENDIF
IF mc(i,1) + mc(i,4) >= Width THEN
mc(i,5) = -ABS(mc(i,5))
ENDIF
IF mc(i,2)- mc(i,4) <= 0 THEN
mc(i,6) = ABS(mc(i,6))
ENDIF
IF mc(i,2) + mc(i,4) >= Height THEN
mc(i,6) = -ABS(mc(i,6))
ENDIF
NEXT i
x = 0
WHILE x < Width 'plot routine
'print x
y=0
WHILE y < Height
sum = 0
FOR i = 0 TO NumCircles
dx = x - mc(i,1)
dy = y - mc(i,2)
dd = dx * dx + dy * dy
sum = sum + (mc(i,3) * mc(i,3) / dd)
NEXT
IF sum > 3 THEN
PIXEL x,y,RGB(0, 255, 0)
ELSE
PIXEL x,y,RGB(0, 0, 0)
ENDIF
y = y + sx
WEND
x = x + sx
WEND
END FUNCTION

FUNCTION RRandom(min,max)
RRandom = RND()*(max-min) + min
END FUNCTION