Masks

today i have tried the masks but it will hard to understand it and while im watching the example i found something weird see this original preview of the example (no edit):

<img src="http://i46.tinypic.com/r79nrk.png" border="0" />

and this after i edited the "sprite" or the construct2 picture (i have just clicked on corp the transparent on edit animation)

<img src="http://i46.tinypic.com/dbgsd5.png" border="0" />

also sometimes it work the effect and sometimes no depend on the layer so what the normal way to use this and why i need transparent on the sprites??

As you can see from the images, areas of transparency are included by some of the effects. To make it clearer what the effect does, the cog has a large area of transparency around it. For example, compare the 'destination in' effects before and after - it's clearer what it does in the original.

so the behind picture must be fully covered?

Is layer 99% transparent same as force own texture? They both activate effects.