Cascading effect on a Gradient lightstrip

I’ve recently installed 5m of Gradient Lightstrip up the side of my stairs, with motion sensors top and bottom.

Ideally, I would like to cascade a light Scene/Effect up/down the stairs, when someone trips one of the motion sensors, then turn off after a set period. In addition, it would need to be dependent upon low light conditions.

Any suggestions on where I would start?

Best Regards