code: private boolean shouldEscapeAsCodePoint(int codeUnit, int index, int firstCodeUnit)
      {
          // If the character is in the range [\1-\1F] (U+0001 to U+001F) or is U+007F, [...]
          if (isInRange(codeUnit, 0x0001, 0x001F) || codeUnit == 0x007F) {
              return true;
  
          } else if (index == 0 && isInRange(codeUnit, 0x0030, 0x0039)) {
              // If the character is the first character and is in the range [0-9] (U+0030 to U+0039), [...]
              return true;
  
          } else {
              // If the character is the second character and is in the range [0-9] (U+0030 to U+0039) and the first
              // character is a '-' (U+002D), [...]
              return index == 1 && isInRange(codeUnit, 0x0030, 0x0039) && firstCodeUnit == 0x002D;
          }
      }
docs: See https://drafts.csswg.org/cssom/#escape-a-character-as-code-point.