* Players are in control of two separate storylines. One features Bowser and his efforts to stop an arch-villain from taking over his castle.
* The microbe-sized Mario & Luigi must muscle their way through challenges and keep their nerve if they want to find a way out. They take action to control Bowser from the inside - but without his knowledge.
* Players can switch between storylines at will. What happens inside Bowser affects what he's doing on the outside. Sometimes Mario & Luigi must solve puzzles and challenges behind the scenes to help Bowser overcome various obstacles and advance the plot.
* Players must make well-timed button presses to enhance their performance during battles and challenges.
