I couldn't tell by the structure of the stairs, but I'm assuming from the posture of the cat that it's climbing up the stairs. The shoulders are more hunched upwards and the back is arched inwards, while if it were climbing down it would be somewhat the opposite ? Or maybe I'm just imagining things.
Up, I can't see the down at all! It's paw looks lifted, & there are those safety grips across the edge of each step, which you'd see from above not below. Although the tail seems to imply it's descending
I say down cause you can't see the edge from top as generally the stairs would be flat and the cats tail is raised for balance which can only mean cat is doing downstairs
THIS CAT IS NOT WALKING EITHER. It's on a horizontal slope because this is an optical illusion. On a weird angle.