This machine can deliver Phineas and Ferb to the core of the planet. Surprisingly, there are habitants at the deep mines of the planet and they are now welcome.
Phineas and Ferb have created the digging machine which can deliver them to the center of the Earth. But your sister, that was following you had been captured by the moles and you have to rescue her. Collect diamond to fix the machine and avoid angry mole. Use a flashlight or the music box to distract the attention of mole and pass further.