Purple
Flexible project boards for designers and product managers
Purple allows you to put all of your design and planning work into one place - whiteboard images, specs, designs, prototypes, to do lists, etc. All of your documents and designs are laid out side by side as if they're posted up on a wall, and you can navigate by scrolling left and right. This all adds a better sense of clarity to the design process - for you, and for those you need to share your process with, like clients, engineers, and even other designers.
