@joppiesaus: do you get a particular error in the debugger? what browser and desktop or mobile?
I am using Lubuntu 18.04, Chromium: "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.121 Safari/537.36" and I also tested it on Firefox "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0", I get on both browsers just a white screen with nothing, no errors in console. I tested on Chrome 85 on my android 10 device and that put out the FBI image!
i added a to catch errors and compiled in debug mode in rewind12_c but i don't see any messages on the screenshot
the shadow mask is much better at hiding the banding artifacts particularly visible while decoding certain colors like cyan
the tape head writing demo is based on http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/tape2.html
the coil was fun to make. i used the toroidal helical coil parameterization from https://demonstrations.wolfram.com/ToroidalHelicalCoils/ to generate a path to extrude along using https://www.npmjs.com/package/extrude-by-path with 4 points per turn
this is beautiful