Good memories! I used to use the Cassowary solver back in the day for planning multi-media presentations where you could specify constraints that were to hold between the different elements of the presentation. Think: "play this audio clip at most two seconds after this other video ended", while the inherent lengths of the elements were only available at run-time.

In addition, you could combine quantitative with qualitative, i.e., Allen-style constraints [0].

This all feels like ages ago to me now, but I suppose >20 years actually is quite a long time.

[0] https://en.wikipedia.org/wiki/Allen%27s_interval_algebra