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I enjoy crafting things that surprise and delight.
The lab area of the site is all Embedded Pens! Szenia has some magic in there to only load them if they are in view, something we're hoping to bake into embeds natively at some point.
Also notice the embeds don't have the normal bar across the top where you switch between the code and preview and such. That's one of the things you can do with a PRO account, along with apply Custom CSS and build an unlimited number of Embed Themes.