Sizes for hollow puzzle stone shadow
====================================

|-------------------------------+-------+---------+---------+---------+---------|
|                               | Gfx16 | Gfx32   | Gfx40   | Gfx48   | Gfx64   |
|-------------------------------+-------+---------+---------+---------+---------|
| Dimensions of the hole [px]   | 8 x 8 | 16 x 16 | 20 x 20 | 24 x 24 | 32 x 32 |
|-------------------------------+-------+---------+---------+---------+---------|
| Size of the inner border [px] | 0     | 1       | 1       | 2       | 2       |
|-------------------------------+-------+---------+---------+---------+---------|

The "inner border" is just the same image as the hollow but with a smaller hole
and with 50% transparency.

The shadow models are just a properly moved black version of the hollow stones
with some unnecessary parts removed. The shadow image must not take into account
the transparent inner border of the stone.
