Simplify the following text for a Grade 9 native English-speaking person.
Original: Counter-Strike ( also known as Half-Life : Counter-Strike , Counter-Strike 1.6 , or simply CS ) is a tactical first-person shooter video game developed by Valve Corporation which originated from a Half-Life modification by Minh `` Gooseman '' Le and Jess `` Cliffe '' Cliffe . The game has been expanded into a series since its original release , which currently includes Counter-Strike : Condition Zero , Counter-Strike : Source , Counter-Strike : Anthology and Counter-Strike on Xbox .
Simplified: Counter-Strike is a first-person shooter video game for the computer .