The bigfoot package codifies æsthetic criteria into fuzzy rule sets and penalties and then minimizes the global badness over a number of choices. The underlying ideas are intuitive to understand, easy to state and appeal to document designers with a basic grasp of mathematics. The implementation, in contrast, is an utter beast in hairy programming techniques and bypasses several of TeX’s mechanisms actually intended for that kind of task while working around the damage of others.
Bigfoot stands apart as a package with regard to implementing a complex optimization algorithm (rather than first–fit or greedy algorithms) on top of TeX’s internal algorithms. Casting its design ideas into working code has turned out to be a frustratingly challenging chore.