Simplify the following text for a Grade 9 native English-speaking person.
Original: Introduced in the 1987 video games Metal Gear , and Metal Gear Solid , created by series creator Hideo Kojima , Solid Snake is a combination of a spy , special operations agent , and mercenary who works for FOXHOUND .
Simplified: Created by Hideo Kojima , Metal Gear is Konami 's main franchise and has sold approximately 26.5 million units as of February 2009 . Introduced in the first game of the series , Metal Gear ( 1987 ) , Snake has appeared in the majority of subsequent games and spin-offs .