It's not based on blackcoin, basically you could say I took the blackcoin core as a model to implement the protocol, but im developping another core with much wider scope, but blackcoin seemed a good model as it implement 3 staking algorithm and pow, and seem robust and reliable , so I took it as a starting point to understand the protocol and how wallets and node are made.
But the purenode is completly different, built totally from scratch in C and assembler with a framework I developped originally for an operating system project, based on micro kernel architecture, so I can tell the code is really entierely from scratch
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I mostly take blackcoin as reference core, in the optic that if my core can interact with it, synchronise blocks and tx, and emit new blocks that are accepted by it, it mean my implementation is kasher, and I guess the black coin core will be used at first the time I finish my core 100%.
But in my mind even dealing with coins is only a subset of the possibilities I want to exploit, like low latency private chain without block reward, or many other things related to crypto.
But still blockchain are big on coins, so good proof of concept is managing a full featured coin with pow and pos, and I took blackcoin as a model to understand the gist of it and test my implementation
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Im still un sure if I should better go wild on creativity on new blockchain features based on my core, or improving compatibility with existing core and protocols to make classic coin on the alt market, the two path are interesting, but for the moment im still focused on implementing the protocols and middleware things, even if it's already quite advanced, I think the first real use as in line with multi coin wallets, decentralized exchange/swapping, and globally middleware for other coins, but I have also plenty of idea to develop on non conventional coin chains, like the raytracing and audio/vidéo streaming in which i already have some experience
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The code of purenode is in the other repository
https://github.com/iadix/purenode Hope it's not too long and answer your question