I've been struggling with this asset a bit. Really nice enemy, but I wanted to separate the skull from the flames to add some GPU effects on the flame layer to give it that dynamic pop in my game. Thats where most of my trouble comes in. The number of frames and which frames are in each folder for animation don't match. Further the frame sizes of your skull with flames doesn't match the frames without. This make aligning the sprite frames with my game object very difficult as I have to correct for each set of frames. Doesn't make for good frame animation! I think your asset needs a redo with all matching frame sizes if it's to work as a game sprite. Very well done, just not very well sliced and organized in the folders.