The ellipse syntax is defined as ellipse( <shape-radius>{2}? [ at <position> ]? )
Based on the css-values definition, it looks like a brace multiplier followed by an optional element is illegal.
Shouldn't it be ellipse( [<shape-radius>{2}]? [ at <position> ]? )
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ellipse( <<shape-radius>>{2}? [ at <<position>> ]? ) |