This library wraps Cassowary JS, a Javascript implementation of the Cassowary constraint solver. As with any JS wrapper, using this library defeats the point of Elm! Goodbye immutability guarantees.
So why did I write this? I was wondering how a high-level Cassowary API might look in a functional language - turns out it looks pretty great (see the examples). The next step would be to implement Cassowary (basically Simplex with some modifications) in Elm. I made a start on this and quickly realised I'm more interested in using Cassowary than I am in the implementation. I would consider returning to it if I can get some help.
Here's a demo of the quad example:
