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It will have two worlds, pve and pvp

Really cool. I think the game can be really Amazing :)

How do you use the Blockchain for the Game? :)

login, smt's, auction house, cash shop, website, forum, and more. This is more of a integration not just purely blockchain. It's not possible to have a real-time gameplay on only blockchain technology so we have to merge the technology.

Pvp requires real-time syncing 1-3 second delays are not acceptable and too long for predicting where a user may or may not be.

What will be centralized:

In-game gold will be centralized
User stats
Weapon stats

Many of these things can be tracked and put on the chain, but it's not what you call a trustless system. Because anyone can post as any app as they want.

So it will be publically verifiable as trades and such are concerned.

But mostly handled on the backend with public Apis for the auction house and such.

The plan looks really good

This is brilliant! Your concept and planning must have been well thought out... Not only is this unique, it's genius!