Post an image or graphic.
Or describe a concept (fill a box with color but it can not have stripes, etc....)
Set the rules. The CHALLENGER sets this and is arbitor.
Set a defined purpose ...example, if you want all the resulting images to TILE as a background for websites, you must specifiy it. If you want people to animate an image, or come up with PURPLE versions, etc specify YOUR challenge. If ANYTHING goes, then say that...
Images posted for challenges should stay up at least a week for people to see/participate. If you want to leave them up longer, fine but realistically, this does use bandwidth of the people that participate so we do not expect these images to stay up indefinitely!
Be aware that some people may want to take the images for use in their own projects. If you do not want this be sure to watermark your images in a way that others can see, but not USE the image without interference. If you don't mind if people use your work in some way, go ahead and state that in your post so there is no question or hard feelings.
These challenges can be a lot of work and a lot of fun. I tip my hat to those who participate and join in when they can!
