the animation of circles with the help of two straight lines of mathematical examples

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    Rem Project: pulsujacy okrag
Rem Created: 2006-05-29 17:46:27

Rem ***** Main Source File *****
rem ***** rozdzielczosc ekranu *****
set display mode 800,600,16

rem ***** wielkosc czcionki *****
set text size 25

rem ***** poczatkowe dane *****
r=90:rad=300:rr#=5:rr1#=0.1

rem ***** glowna petla programu *****
do
cls
set cursor 20,20:print rr#

x=rad+r*cos(i)
y=rad+r*sin(i)

circle x,y,rr#:circle x,y,rr#-20

i=i+1:ii=ii+1:rr#=rr#+rr1#

if rr#>400 then rr#=10

loop