You may or may not be aware of this, but the first Proof of Burn idea came around in 2012, and the first implementation was done on a colored coin clone called Slimcoin. I played a bit with it in 2017-2018, but ended up looking in other places (Hive being one of them). The theory behind Proof of Brain is still interesting, though. Here's a starting point: https://github.com/slimcoin-project/Slimcoin/wiki