I'd seen this article a while ago after noticing many ZX Spectrum screenshots have this attribute e.g. https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvX

I'd seen this article a while ago after noticing many ZX Spectrum screenshots have this attribute e.g. https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhc-L6UISyvuM5XEAlQrQvFMfH_wnk7va4HtuicGPNfwkErrmsmHuihSRsWlO4lGOj-MfgO_Yra7IrD5QT0UhTEngLWO-76y2VOoz81-rIIS-fcG8Dn2WMubvnrEFp-JZgON8xFAe3DBSp7TqTO6YMegLslQgk_leRKOzM0STe2AOkwVe13YEXRR2RB/s1280/zxspectrum3.jpg https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh... Other colours also have intermediate depths when arranged on black, so I suspect a depth based 3D image converter may be possible "3D without the glasses", but never found the time to write it.