High Quality Content by WIKIPEDIA articles! The Sentinel is a computer game created by Geoff Crammond, published by Firebird in 1986 for the BBC Micro and converted to the C64 (by Crammond himself), Amstrad CPC (with a cross-compiler written by Crammond), ZX Spectrum (by Mike Follin), Atari ST, Amiga (both by Steve Bak) and PC (by Mark Roll). It was released in the US as The Sentry. It was among the first games to feature solid-filled 3D computer graphics on home computers. While it ran acceptably fast on 16-bit computers, it was slow on 8-bit machines such as the C64, where the next view took up to three seconds to be precomputed. Despite this, the game retained a dedicated base of fans, some of whom were able to modify their computers to enjoy it better (for example, by using a CMD SuperCPU in a standard 1-MHz 6502 Commodore 64 to achieve CPU clock speeds of 20 MHz).