Xiao Xiao No. 4 is the fourth installment in the Flash web series Xiao Xiao, and the second interactive feature. It is a short rail shooter-type game, where the player moves with a gun through the enemy base along a predefined path, quickly shooting all the enemies that pop up before his health is completely depleted. Sometimes the player must also shoot down projectiles launched by the enemies. There are six bullets in the player's magazine and once they run out the gun must be reloaded by pressing Space. There are three difficulty levels available, each granting the player a different number of lives.