CodePen.io is an online code editor that allows you to develop in an open-source environment. You create 'pens' which display a live-preview as you code which is great for testing out bugs, collaborating and discovering the latest design patterns. CodePen supports a great selection of languages, frameworks and libraries which you can quickly spin up into a pen to get coding on straight away.
Listed below are 20 awe-inspiring CodePen examples you can learn from. Make sure you take the time to read over the code and compliment the user by hearting or leaving a comment on the pen.