CLS
SCREEN 9
DIM pnts(3, 2)
                                             
pnts(1, 1) = 150: pnts(1, 2) = 30
pnts(2, 1) = 30: pnts(2, 2) = 1000'300    
pnts(3, 1) = 1000: pnts(3, 2) = 1000'300  
x = 100: y = 100
                                                  
FOR i = 1 TO 3
  PSET (pnts(i, 1), pnts(i, 2)), 15
NEXT
                                             
DO
  rndpnt = INT((3 - 1 + 1) * RND + 1)
  x = (x + pnts(rndpnt, 1)) / 2
  y = (y + pnts(rndpnt, 2)) / 2
  PSET (x, y), rndpnt + 2
IF INKEY$ <> "" THEN END
LOOP