A free program for Android, by 41MobilApp.
Counter-Strike is a series of tactical shooter games on PC where a team of terrorists and counter-terrorists fight each other to bring either chaos or order. This franchise began in 1999 and became popular in the 2000s. To this day, its latest installment is still considered to be the most popular game in the world.
However, if you want to play something similar on your mobile device, then C.Strike: WAR Online is the way to go. This has the same mechanics as the Counter-Strike series.
To play this game, you must join a room or create one. You must also choose to be on the terrorist or counter-terrorist side.