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Home Page for the tool: giffyglyph.com/monstermaker/
The system the author is introducing substitues Monster Points for D&D 5E's rather bastardized CR ratings for building challenging encounters. It also provides an easy to use custom moneter building UI that crafts useful monster cards.
Overall this seems like amazing stuff. Something that I look forward to using. So much so I have added a link for the app to the side bar in the DM section.