linear-gradient value doesn't seem to support 'to left', 'to right', or 'turn' values 

See https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient()

If my initial value is `linear-gradient(to right, #ffffff 50%, #000000 100%)` the popver shows `NaN` for the degrees.

`0.5turn` is also not supported - it is interpreted as `1deg`.

I find `to left`, `to top` syntax more readable. Can it be supported?