This page will contain many prototyping tools and design helps.

Origami
A Free tool to create Modern UI , Can export codes snippet to share with engineering.

It’s really easy to make digital prototypes, even directly from your paper sketches. Apps like Marvel or Pop App provide a simple way to photograph your drawings, and link them together with hotspots. You can even import Photoshop or Sketch images into them. These tools are useful for quick iterations of the flow of the screens, but lack a certain fidelity in interaction, in a way that they are limited in transitions, gestures and motion. And that’s fine as long as you are not occupied with the interaction itself, but still are looking for the the right flow of actions and feedback a user will get. Some tools are more comprehensive for these tasks, like InVision, Proto.io or Flinto.

Illustrator Tutorial

Basic features of illustrator demonstrated by  Karolina in our Stanford Crowdsource Project