Early this year Thekla Inc. successfully released The Witness after a lengthy development, and now developer Dustin Long has created a "demake" version of the game for the Nintendo Entertainment System, The Wit.nes, as a "reinterpretation and tribute" of the original work.
What's neat about The Wit.nes demo (which currently encompasses only the starting area of The Witness) that Long posted to itch.io today is that it's a ROM that could conceivably be flashed to an NES cart and played on an actual NES.
Long has been developing his own NES ROMs for some time, and often posts NES development analyses and lessons learned on his personal blog.
For more insight on the topic, check out this 2013 talk from Vblank Entertainment's Brian Provinciano about how he crunched his modern game Retro City Rampage down to get it running on an actual NES cartridge.