Opengen 0.10.0a2 (preview, RFC)

Main changes: documentation available on the website, simplification of Cartesian products of multiple rectangles and sets $\{0\}$, more unit tests, number formatting when printing OcpSolution. Default penalty update parameter is now 1.75.

Full Changelog: opengen-0.10.0a1...opengen-0.10.0a2