It adds a stylesheet to accept new stylerules. For every element set (CSS selector) you want to watch it adds a new stylerule that makes a no-op animation happen (transform:none -> transform:none). Every time such a node that matches your selector is added to the document, this animation is triggered. When this happens, Sentinel publishes an event to whatever handlers you ask it to, by listening to the 'AnimationStart' event emitted when an animation happens. Pretty clever, but simple, and I think this is not the first source to suggest this approach for watching DOM modification. Note, the unminified dist/sentinel.js is not 682 bytes!

Looks like it adds a keyframe animation to the elements, and when a child node is inserted that animation is triggered, and emits an event.

Am on my phone tho, so may have misread.

From the code, it adds `animationstart` event that will be fired for any newly injected DOM https://github.com/muicss/sentineljs/blob/master/src/sentine...

It adds a faux `animation` keyframe for the specified CSS selector.