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NXEngine
A port of the open-source rewrite Cave Story game engine for various platforms. Original author is Caitlin "rogueeve" Shaw, https://nxengine.sourceforge.io/
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InfluxDB
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On top of what u/alulalol said, there is an open source reimplementation of Cave Story, called NXEngine. Usually, you'd use it through the libretro port.
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