You have a regular gun to shoot the gun drum. The more of these you fill, the better you can evolve, and at the end of the level, a new pistol awaits you! Unlock new weapons and gloves, earn money to pass more difficult levels, and upgrade various traits, such as the rate of fire. The further you advance, the harder the obstacles get in your way, right up to the enemies shooting at you. Not all hurdles can be passed if you’re not sufficiently upgraded, but that’s not a problem, because the game is balanced and gives good opportunities to improve.