It seems to me that the shape of the triangles make the shape of map, this changes the collsion detection as i assumed a grid of triangles(like a tilemap). You will need polygon collision.

Have a look at: http://gpwiki.org/index.php/Polygon_Collision

And: http://gpwiki.org/index.php/VB:Tutor...sion_Detection

You first want to do a circle circle collision check for visible triangles
If that collides you want to do a triangle triangle check

If delphix has native collision components do use them!