font-FiraCode/features/calt/cross.fea

### 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;