How to keep 2D character facing the direction it was in(right/left), when it is moving up/down?

Hello.

My character has 2-directional animation (right/left), but it can move in 4 directions (right/left/up/down). I'd like to learn how to keep it facing the direction it was in, when it is moving up or down. This is a script I am using: alt text As for an Animator, I tried a few options to see if I can get the idea working without modifying the script but with no success. Currently, I set both 'Idle' and 'Walk' animations to simple 1D Blend Trees with Transition conditioned by 'Speed' parameter: I suppose, I could take all the Blend Trees apart and make transitions that would link to the correct animation but that would get very messy, when adding also 'Hit' and 'Attack' animations.