Step-down reaction

I am me, and then there is my shadow.

Following me, grazing the ground I once walked on,

And perpendicular to it am I,

Not me anymore, I am the shadow of my shadow,

Buried inside that ground my shadow grazed.

I am me, and then there is my shadow, and then there is the shadow of my shadow.

I step down on the staircase of my own shades.