1) Copy protection 
Lenslok™ is a copy protection mechanism found in some computer games and other software on the 8-bit Atari computers, Commodore 64, Sinclair ZX Spectrum, Sinclair QL, MSX and Amstrad CPC. The most famous game to use it was Elite for the ZX Spectrum. The Lenslok device was essentially a row of prisms arranged vertically in a plastic holder. Befor...