Skin Image
To make a skin file you must first create an image file. This can be a PNG file, JPG file, GIF file or a windows BMP file with at least 24 bits color depth. PNG is the preferred format. The skin image will contain all the square images needed to make a complete skin. The images are placed side by side.

The size of each image can be any number of pixels, but a size around 100x100 is reasonable for a PNG image and 50x50 for a BMP image. A larger size gives nicer graphics but larger skin file and a smaller size doesn't look so good when enlarged. You can use any image editor (Photoshop, PaintShop or any other) to create the skin image.

The total number of images needed depends on the following choices:

• Floor: Two images, one for plain floor and one for goal.
• Package: Two images, one for package on floor and one for package on goal.
• Sokoban: Two images, one on floor and one on goal. Can be complemented by two sets of four images, one for each direction (up, down, left and right) both on floor and on goal.
• Wall: One or sixteen images. One for simple walls or sixteen for connecting walls. In the case of connecting walls one more image can be used to cover the top of four neighboring walls (see Wall Top below).

The order of the images is not important. The Classic skin looks like this in the skin tool.



Transparency
The images can be made transparent, this is useful for the package and Sokoban images. When a package or Sokoban passes from floor to goal and is halfway between, it looks much nicer if the image is transparent.

Transparency is controlled by the Transparent parameter in the skin file. The color of the bottom left pixel of the image is the color that will be transparent. Transparency can also be used to reduce the number of images needed. If the Sokoban image is transparent, you could use the same image for Sokoban on floor and on goal. I choose to use separate images in the classic skin because some of the background color will show around the edges due to antialiasing.

Wall Top
The Wall Top image is used to cover the hole that appears when four walls are placed in a square. The left image is without Wall Top and the right is with. Wall_Top_X specifies how much to offset the image to the right and the Wall_Top_Y gives the offset downwards.

Background Image
The background is what is shown around and outside the actual level. It can be specified with the Outside parameter which indicates one of the pictures in the Skin image.

A background can also be a separarate image with a different (larger) size than the pictures in the skin image. Use the Assign External Background function to include a background image and the Imbed External Background function to make it imbedded in the skin file. The background should be a tiling picture.

Skin Tool
The skin file is a text file. It can be created with any text editor, but easiest is to use the Skin Tool. Use New or New from Template to create a new skin file. You can also open an existing skin file and use Save As to give it a new name and then start to modify it. Now, you must assign the image you created. Make sure you saved your image in the same folder as the skin file. Use Assign External Skin to connect the image with the skin file. Please note, that the skin now consists of two files, the skin file and the image file. It is a good idea to have the image external during the design of the skin, this makes it easy to modify the image, save it and immediately run the game and see how the skin looks.

When you are satisfied with the design of your skin you should use Imbed External Skin to imbed the image within the skin file. Use View Images to see the image. On top of the image window, you can see the numbers of the individual images. Use these numbers as parameter values. Below each image is a checkbox, check the box to make an image transparent. The size of the images is shown to the left.

The next step is to edit all the values in the skin file. Fill in the Description part with the appropriate values. The skin section contains the values that identifies the individual images. See the Skin Reference for a complete description of all parameters. See also Skin File Format for an example skin. Next use Validate Skin to make sure there are no errors. Run the Sokoban game and select your skin to see the result of your work, just make sure you saved the skin file in the path specified in the game options.