REM Planetary type Ellipses, RG Weston, 27.12.2002
      MODE8
      PRINTTAB(4,0)"Press a key to get next elliptical planetary orbit, or hold down for many"
      delay=INKEY(100)
      GCOL0,1
      ORIGIN 640,512
      REPEAT
        n=n+1
        col=n MOD 16
        IF col=0 THEN col=1
        IF col=8 THEN col=9
        GCOL0,col
        T=RND(360) :REM angle of ellipse axis to the x axis
        a=20+RND(250):REM semimajor axis
        e=RND(999)/1000 :REM eccentricity
        PROCellipse(a,e,T)
      UNTIL 0
      END
      :
      DEF PROCellipse(a,e,T)
      PLOT69,0,0
      b=a*SQR(1-(e^2))
      COLOUR col
      PRINTTAB(4,2) "Semi-major axis = ";a;"   Eccentricity= ";e,"Angle= ";T;" deg";SPC(3)
      FOR t=1 TO 360
        REM ellipse centred on origin
        x= a*COSRADt
        y=b*SINRADt
        REM shift centre to the focus
        xx=x+(a*e)
        yy=y
        REM Rotate point by angle T
        xxx=(xx*COSRADT) + (yy*SINRADT)
        yyy=-(xx*SINRADT) + (yy*COSRADT)
        IF t=1 MOVE xxx,yyy
        DRAW xxx,yyy
      NEXT
      G=GET
      ENDPROC