The cornerstone of the Rub-a-Dub concept is the Rub tool. The Rub tool is activated by holding down the left mouse button and moving the cursor in the image area. Doing so reveals portions of a second image that is stored in a layer beneath the original image. If the image on the screen is a black and white line drawing, using the Rub tool causes colors to appear as if by magic. If the image is already colored, additional detail may emerge or the colors may change as in spring to winter or day to night. Using the Rub tool to color, combined with the element of discovering hidden imagery appeals to children's curiosity. Moreover, it is a simple process requiring minimal skills and yet yields results that sustain their