Thank you igortyhon.
that's exactly what I was looking for. But I can't figure out how it works. the sprite skeletton goes translucent on your project but when I do the same on mine, it is visible on source atop blend configuration. I've c/c the skeleton sprite, that still visible on my project. why does that happen?
Check out the blending modes in the sprite or layer.
Actually, the construct has many such modes, you can also look at this example.
editor.construct.net
I don't use it often, so I have this cheat sheet.