If you replace CommandConstruct with this, you can lazily calculate the values when needed, so you don't need to do redundant work
```rust
#[derive(Clone, Copy, Debug)]
struct RawCommand(u16);

impl RawCommand {
    fn reg_x(self) -> Reg {
        let nibble = (self.0 >> 8) &0x000F
        Reg::from_nibble(nibble)
    }
    fn reg_y(self) -> Reg {
        let nibble = (self.0 >> 4) &0x000F
        Reg::from_nibble(nibble)
    }
    fn val4(self) -> u8 {
        self.0 & 0x000F as u8
    }
    fn val8(self) -> u8 {
        self.0 & 0x00FF as u8
    }
    fn val12(self) -> u16 {
        self.0 & 0x0FFF
    }
}
```