Marvel's mobile companion app is probably the tool's coolest feature. If you're a designer who loves starting projects on paper, the app can turn your sketches into prototypes just by taking a photo. Your photos are automatically synced with your Marvel account, allowing you to quickly create mockups to experiment with before even designing a single layout in Photoshop or Sketch.
Not only is Marvel simple to use, but it's also simple to learn. Their website is complete with FAQs, video and written tutorials, as well as a regularly updated blog. Marvel is also home to a thriving community of designers who regularly share their prototype designs to help inspire the workflows of others.
While the simplicity of Marvel may limit the functionality desired by some designers, its low barrier to entry and companion app makes it the perfect tool to get up and prototyping quickly.