Chose this option to challenge yourself and build the fully-working demo on your own, on the stage. Warning: live-coding ALWAYS causes problems - you'll forget about the semicolon, will mistakenly delete the closing bracket, the browser or the editor will freeze or something like that. You're doing that on your own risk.
You can live-code the game in your favourite editor and show the results locally in the browser, or use the JSFiddle for that:
Introduce the Canvas element, show the initial piece of code you're gonna expand and then present the next logical steps when building the demo game: drawing on the Canvas, movement, collision detection etc. Help yourself with the tutorial articles to master the flow if needed.
If you're unsure if you want to do live-coding on stage you can pick the usual approach with the slides containing code snippets and do that instead. It's the secure way to present the topic as everything is under control.
You can also go back to the Content Kit's index page.