Rex is a shoot 'em up video game published by Martech in 1988 for the ZX Spectrum and Amstrad CPC.
The player controls Rex, a 'rino-sapien' mercenary, hired to eliminate the humans that have built a Great Tower in a place called Zenith. Action takes place in a flip-screen platformed cavern complex – Rex can jump, shoot and activate a shield to block incoming attacks. Enemies include fixed gun turrets and human soldiers; shooting the latter initiates a 'multi recoil system' in which the defeated soldier's body continues to recoil until the player's bullets stop hitting it. Destroyed enemies leave behind Energy Bubbles, which can be used to upgrade Rex's weapon.
Rex was a critical success, with Your Sinclair awarding 9 out of 10, CRASH awarded 82% and Sinclair User awarded 88%. The difficulty of Rex is highlighted, drawing comparisons with Cybernoid, but reviewers were also impressed with the intricate graphics and level of action.
Rex was developed by a programming team consisting of Neil Harris, Richard Allen and John Anderson. After working for IBM, they all left to form The Light, choosing the Z80 as their development platform. Neil and John were coders, whilst Richard worked on graphics. Rex was the only game they developed.
Source: Wikipedia, "Rex (video game)", available under the CC-BY-SA License.