The gameplay of Mario & Luigi differs from most other role-playing games due to its focus on controlling Mario and Luigi simultaneously. During overworld sections, the directional pad controls Mario's movement with Luigi following closely, while Mario and Luigi's other actions are controlled individually with the A (Mario) and B (Luigi) buttons respectively. The game begins with them being able to jump independently, though they would soon gain access to hammers and a variety of other techniques as the game progresses. For example, Luigi's hammer can be used to squash Mario into a smaller size, allowing the latter to access small gaps, while placing Mario on Luigi's shoulders allows them to act like a propeller and hover across large gaps. Various enemies roam the overworld, and coming into contact with these enemies initiates a battle. Landing a hit on the enemy while on the overworld allows the player to deal pre-emptive damage, while the opposite is also possible.