I see someone negrepped me.
If only I knew who did it, I could negrep him/her back in turn!
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Another good thing could be making 3 different tileset parts:
Layout/Parallax (16 bit colors)
Translucency/Alpha (Grayscale)
Mask (Grayscale, 0.5 is something like ooze, can be used along with water blocks)