This is pretty sweet using a desktop browser, but the animations can be a little choppy on mobile. Is this more because of how mobile browsers work or are there parts of the library that can be improved performance wise?
this does not work with time based animations right?
A tool that would be really nice for developing time based animations would be one where you could switch easily between time and mouse movement.
It works for any measurement! That choice is left completely up to the user. Instead of wrapping it in an event handler, you might instead set a variable for 'start time', run animations on requestAnimationFrame, and pass in the current time.
Just an FYI, the scroll-hacking on the home page doesn't work with arrow key or hotkey based scrolling (for example, vimium or vimperator extensions for j/k key scrolling) - obviously a small subset of users, but I know a lot of non-dev users that use arrow keys or page up/down to scroll on web pages too.