So. Books have covers, right? Well, yes, but actually no.

Books are tricky business. If the book is self published then it might not have a cover or an ISBN. Other times a book might be incredibly old and never really had a cover to begin with.

No one is going to make covers for these books, but that doesn't mean we can just leave them naked & coverless. We want to create a beautiful UI so we have to show something.

So that is what we do. We will, given the same input arguments, always create the same cover on the fly. It will obviously not be a "real" cover, but it's better than nothing or just a gray cover.

The covers have some variation. Each cover can be broken down into multiple pieces.

A cover (might) have a unique color. It can be the following.

• Gradient based on input hash
• Static predefined color

Details have predefined placement, but it still has the following variance.

• Top (left, center, or right)
• Bottom (left, center, or right)

We generate a flow field based on the input hash. This affects the pattern.

There are the following patterns we can draw.

• Circle
• Waves