Cave Story 3D, commonly referred to as CS3D is a 2.5D remake of Cave Story by Nicalis for the Nintendo 3DS, released in 2011.
While there are some minor differences - notably TSC files being âSJSâ instead - its engine uses the exact same files as freeware, and is thus (technically) compatible with (some) editors, allowing it to be modded. However, due to lack of interest, there is little to no documentation around it, nor have any mods been released outside of a proof-of-concept video.
We at the Cave Story Modding Wiki would never stoop so low as to condone the pirating of a 10+ year old game that only ever had a physical release on a now-obsolete console. However, those interested in modding it will have to source a ROM either by dumping their legally owned cartridge or with the assistance of their favourite search engine.