Knock'em All is a casual, first-person shooter that tasks a player to knock down robots and other enemies that appear before them on platforms in different environments. The player might also need to save an innocent, which merely means that the enemies walk toward a bystander instead of toward the unseen player.
The best way to knock down various enemies permanently is with explosions. If the player shoots a robot in the head, for example, the head explodes. If they shoot the body, the robot just gets back up again. The game also provides objects that explode, such as red barrels.
Over time, enemies that don't have explosive heads appear and increase the challenge. For example, the player might face off against a boss that rolls red barrels at them. They can only knock the boss down by repeatedly exploding the barrels close to him. The player knows if they've defeated an enemy because the game automatically moves them to the next platform on their way to the finish area. During a boss fight, every successful hit is usually marked with a jump to a different position in the battle arena.
Knock'em All provides unlimited basic ammo. Each gun also charges over time to supply the player with a limited number of explosive rounds. When the player clears a level, they receive coins to upgrade the gun's strength, power and fire rate. They can also eventually upgrade to other guns after they reach specific levels. If they watch an advertisement, they can increase the number of rewarded coins.