I find circles a very difficult shape, especially as they become smaller. I usually start with a template - e.g. the 2 speedos and work inside or outside those:
Source: https://ascii.co.uk/art/circle
%%% %%% %%% %%% %%% %%% %%% %%% %%% %%% %%% %%% %%% ...
..... _d^^^^^^^^^b_ .d'' ``b. .p' Objects `q. .d' in mirror may `b. .d' be less virtual `b. :: than they appear. :: :: ....................
Depending on your screen characteristics they will look like: perfect circles horizontal ovals vertical ovals
CIRCLES ==========================================================================
=========================================================================== , ___ _,_ _, _, _ _, _ _ _,_ __, __, _, _, __, , _ / | | |_| / \ |\ | |\ | | | / |_ |_...
_ _ _ ,="`/ / /'=. / / / / / / /'. /_/_/_/_/_/ / / \ _.='/ .-' - _ - _ -`"-,/ /\ .'_.='/ / -_ - _ - _ - _ -\/...
. . ): /.:) (:./ )( (.;) _)/ |:| |;| |:| .';'. /` ....
____________________/%%*%%*%%*%%*%%*%\____________________ //~~~~~~~~~~~~~~~~~~ I\ | ___ | ~~````~~~~~~~~~~~~~~~~~\\ I: | I \ | (__ | O f f i...
. .-"~~~"-. /(-_`.\| ;\ |'? / .(-| | \,`_ ,- | \ ( \ `,/ `-./,'.-' __.-|-.__ """"""""" unknown