In a top-down view of a town, take to your guns and shoot down the enemy.
This game seems to be based, or at least modelled on Omar's Oyster Outing, except without the story, impetus, reason to keep playing, goals and objectives... you get the picture.
As far as actual gameplay or story goes, there is none. Nobody explains who you are, who they are or why any of you are there. It is not defined who the bad guys are, it is not defined who your friends are. All you know is the terrorists have to die while the citizens stay alive.
On the left side of the screen, a long and quickly updating list of recent events scrolls past. Sometimes these occur at the same time as you doing something. They usually repeat that a citizen, policeman, or enemy has been killed, and a point ranking for each. But its impossible to see which is yours as they all come up so fast.
Its strange and really not worth playing... but if you want to try unlocking the mystery of the game and find out what you actually have to do and how to do it, good luck.