I have a fair method for investors will publish in due time but currently in talks with another group that wants to license it to be first-to-market.
Either way, it appears likely to be open-sourced.
pevpot had an extremely robust system that would make it provably fair for investors:
https://web.archive.org/web/20151213003346/https://www.pevpot.com/provably-fairBut like all on-chain games, is doomed by a poor UX