Hi, it's not immediately obvious in the software but if you select a few sprites, e.g. the idle sprites, you can type 'idle' in the file name prefix field and the app will assign that prefix to those sprites when it writes them out. You can do this for any one or more of the sprites in the sheet, so for example all the left facing characters you can select and set the prefix to 'left' and the output will be left_0.png, left_1.png, left_2.png etc. Does that cover what you are referring to?