Flipping tiles

[Murrit]

Hi All

I've been trying to replicate a flipping card compund that i saw in the forum, and I've managed to get it to work on a flat grid. But now i'd like it to work on a deformed grid.

The problem I'm getting is not alighning the particles to the surface, but alighning their local axis, so that their Y orientation points in the same direction to that of the surface emitter's Normal.

I hope that makes sense, please see attached scene file...

thanks very much for any help