Shadow Flutter

Update:  My cat remains intrigued by the body-length mirror I placed at the top of the stairway.  Now when I'm going downstairs he races past me to stand in front of the mirror and watch me descend the stairs.  He's no longer freaked by my being in two places at the same time; he takes it as a given.  I've also caught him looking at it from different angles.  He looks like he's figuring out how much territory he can peruse by changing his angle of view.  I'm waiting for the day I catch him cleaning himself by looking in the mirror.

So how smart are cats? I put a body-length mirror at the top of the stairwell yesterday, and my cat, Romulus, is fascinated by it.  First time he saw it he stood starting into it; I think he realizes he's looking at himself and is fascinated by the idea of it.  Enthralled, his tail flips left and right in strong strokes of inquiry.  But what really got him going was when I walked up the stairs.  First my head appeared in the mirror, then my shoulders, then slowly the rest of my body as I reached the top stair.  Now I'm in front of him and behind him at the same time, and he freaks.  I never saw him display such frenetic energy as he displayed while trying to figure out what was going on.  How could I be behind him and in front of him at the same time?  Looks to me like he recognized both of us.  He would probably have quite a time of it if I took him to a hall of mirrors.  Imagine a cat looking at its reflection in a convex or concave ...