font-FiraCode/features/calt/cross.fea

lookup hexadecimal_x {
  ### 0xFF
  sub [zero zero.zero] x' [@Digit @HexDigit] by x.multiply;
  sub [zero.tosf zero.zero.tosf zero.tosf.zero] x' [@DigitTosf @HexDigit] by x.multiply.tosf;

  ### 800x600
  sub @Digit x' @Digit by x.multiply; 
  sub @DigitTosf x' @DigitTosf by x.multiply.tosf;
} hexadecimal_x;