Gravity center on toolchain editor tends to the up-left

When you displace a block at the toolchain editor, the next place the block will assume is shadowed in green. Currently, the algorithm to calculate this tends to place the block on the left-upper closest location. It would be more intuitive if the location would flip to the right or down part when crossing the middle line between two-points.

Furthermore, it would look more like a shadow if the projection was greyish instead of green.