According to the designers, the design for an icon or logo is subtly different at different sizes. For example, the design for 20 point icon or logo will be the same for 6 point or 120 point. So, if you want to get different designs for different font sizes, you have to create a duplicate icon from the font file and set the appropriate glyph. You may give background colors, but when it is about multicolored icon, it symbol font cannot help you in that case.
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