In MachineGunner 2, you will control four players. You can use WASD to move them, and Arrow keys to fire. Use Q,E,R,F to Mark or Unmark player 0,1,2,3. Marked player is able to move but Unmarked player's position is locked. 

Also, you can place your players to Cover Block. When player collides with it, Soon the player's color will be turned into grey. In that state, the player is invincible. But it can't fire.

When you exit the Cover Block, the player turns back to original state.

You should fire to the enemy that has same color with your player. Exceptionally, white enemy

takes damage from all players' bullets.

One hit will take you the start of the stage, so try not to get hit. If you don't want to be game over in some stages, press f12 to activate playerkeepGoing mode. If you see texts on the left down side from screen, it is activated. you can press f12 once again to deactivate it or when going next stage, it will be deactivated automatically.