Implementing decorated footnotes in Context

I’m trying to implement a colored footnote style with Tikz in Context. After some fine tuning according to the specific font in use, I’ve gotten something like this:

As one can see, the circle sizes don’t fit double-digit numbers well.
I’ve tried to come up with a circle size that would fit both single- and double-digit numbers, but the ideal would be for the circle to "expand", perhaps inserting the footnote number inside the Tikz node. Another option could be to set the size according to number, with an if ... else ... fi construction (cannot figure out how to do that, either). If there’s an easier solution with Metapost, I’ll gladly use it.

setupbodyfont[palatino,10pt]

usecolors[crayola]

usemodule[t-tikz]

%definefontfeature[f:sups][sups=yes]
setupnote    [footnote][textcommand={tikz[overlay]fill[MagicMint] (.5ex,.8ex) circle (1.4ex);},
%textstyle=addff{f:sups},
textcolor=Scarlet]
setupnotation[footnote][way=bychapter,
numbercommand={tikz[overlay]fill[MagicMint] (.5ex,.8ex) circle (1.4ex);},
%headstyle=addff{f:sups},%headstyle={ssbf},
headcolor=Scarlet]
setupfootnotes[rulecolor=TropicalRainForest,rulethickness=.8pt]%

setupfootnotedefinition[
alternative={left,bottom} % where to set the footnote, comment it to leave it inside the margin
hang=fit, % if commented, hanging is larger
indenting={yes,small},indentnext=yes, % please, indent everything
]



starttext
chapter{One}
dorecurse{12}{footnote{}}

chapter{One}
dorecurse{12}{footnote{}}

stoptext

%setuppapersize[A5]
setupbodyfont[palatino,10pt]
usecolors[crayola]
startuseMPgraphic{blackbird}
numeric Offset, Size;
Size := OverlayWidth;
%Without an offset circles look too small
%Change ad libitum
Offset := 0.1EmWidth;
fill fullcircle scaled (Size + Offset) withcolor "MagicMint";
stopuseMPgraphic
defineoverlay[blackbird][useMPgraphic{blackbird}]
setupnote[footnote]
    [textcommand={framed[frame=off,background=blackbird]},
    textcolor=Scarlet]
setupnotation[footnote]
    [way=bychapter,
    numbercommand={framed[frame=off,background=blackbird]},
    headcolor=Scarlet]
setupfootnotes
    [rulecolor=TropicalRainForest,
    rulethickness=.8pt]
setupfootnotedefinition
    [alternative={left,bottom},
    hang=fit,
    indenting={yes,small},
    indentnext=yes]
starttext
startchapter[title=Uno]
dorecurse{12}{Texto footnote{Nota a pie de página} }
stopchapter
startchapter[title=Dos]
dorecurse{12}{Más texto footnote{Otra nota} }
stopchapter
stoptext

setupbodyfont[palatino,10pt]

usecolors[crayola]

usemodule[t-tikz]

startsetups bola
ifnumrawcountervalue[footnote]>9
tikz[overlay]fill[MagicMint] (1.1ex,.8ex) circle (1.6ex);
else
tikz[overlay]fill[MagicMint] (.5ex,.8ex) circle (1.4ex);
fi
stopsetups


%definefontfeature[f:sups][sups=yes]
setupnote    [footnote][textcommand=setups{bola},
%textstyle=addff{f:sups},
textcolor=Scarlet]
setupnotation[footnote][way=bychapter,
numbercommand=setups{bola},
%headstyle=addff{f:sups},%headstyle={ssbf},
headcolor=Scarlet]
setupfootnotes[rulecolor=TropicalRainForest,rulethickness=.8pt]%

setupfootnotedefinition[
alternative={left,bottom} % where to set the footnote, comment it to leave it inside the margin
hang=fit, % if commented, hanging is larger
indenting={yes,small},indentnext=yes, % please, indent everything
]


starttext
chapter{One}
dorecurse{12}{footnote{Footnote.}}



chapter{One}
dorecurse{12}{footnote{}}

stoptext