It's been brought up here before but relevant again in case you missed it the first time. The original developer for R-Type for the ZX Spectrum wrote up a deta

It's been brought up here before but relevant again in case you missed it the first time. The original developer for R-Type for the ZX Spectrum wrote up a detailed story of the technical challenges for developing the game. Shaving cycles off to make action smooth was what it was all about. IT'S BEHIND YOU: http://bizzley.com/ http://bizzley.com/