entry smash 378: puzzling chair shadows

sometimes i see a nice shadow and take a few photos then forget about it forr a long time. this is one of those. the shadow is quite remarkable with the lines going in all directions. typically i take a shot including what is causing the shadow unless i want it to remain a mystery.

and sometimes even when the shot reveals what is casting the shadow it doesn't seem to make sense. after studying the image. there are four foldable chairs and a parasol stand without the parasol. one chair is clearly visible but just the backs of the other three are visible, lined up at the edge of the photo. so the three boards of the three chairbacks are casting their shadows roughly lined up on the tarmac while the chair behind them is casting shadows of both the back and seat at an angle to the others. there's a bush and a picket fence etc also so everything is accounted for, right??

well no because the middle of the three chairbacks is clearly casting its shadow partly onto the back and partly onto the seat seat of the chair behind it. and that seat has the shadow of 2 chairbacks not just one. can somebody please explain what is going on because i can't figure it out.

aren't shadows fun?!?