Note: This video demonstrates the particular features in the previous version of Proto.io.
While the primary use of Proto.io is a multi-screen interactive animation tool, the recent asset drag and drag capability makes it great as a hot spot linking tool for full comps (simply drag in a new comp with the same name to replace it throughout the prototype). Plus, Proto.io makes a great wire-framing tool, as you can create a full range of shapes (with any level of fidelity), and then link the screens together. So, Proto.io is great for multiple stages of the design process – allowing you to create a full range of assets, and progressively increase the visual, interaction, and animation fidelity all within the same tool.