Although this is a casual game with sophisticated systems, I feel that the gameplay is rather weak. After playing for a while, the content of the game is not enough to make me addicted and is not a good choice for killing time.
Simply put, you move your character up & down, and shoot the enemy until you defeat them through quick reaction. The gameplay is simple and easy, but it lacks playability. Besides the gameplay, you can choose enemies of various difficulties, get bounties, and upgrade your characters and weapons. This is what the game is about.