roll20-character-sheets/backbone/source/assets/scss/placeholders/_sizingAndRatio.scss

%circle{
  border-radius: 50%;
}
%ratio1_1{
  aspect-ratio: 1/1;
}
%sizesAndRatios{
  .ratio1-1,
  .sheet-ratio1-1{
    @extend %ratio1_1;
  }
}