A new release of Cave Story: Doukutsu Monogatari has been released for AmigaOS 4.1 and offers several new improvements. Cave Story takes place within the cavernous interior of a floating island. The island is populated by Mimigas, a race of sentient, rabbit-like creatures. A particular species of red flower that grows in the island causes the normally peaceful Mimigas to fall into a violent frenzy when ingested. The island also conceals an artifact called the Demon Crown, which has vast magical powers. An army of robot soldiers was sent to the floating island on a military expedition, seeking to harness the Demon Crown as a weapon for wars on the surface world. These robots slaughtered Mimigas indiscriminately in their search for the crown, but were defeated when the Mimigas decided to eat the red flowers as a last resort. Shortly before the game begins, Professor Booster, the Sakamoto family, and various assistants formed a scientific party to research the island, but they became stranded when their medical doctor managed to acquire the Crown: he then forced the expedition to search for the red flowers. The player controls the on-screen character directly using the keyboard or gamepad. The player progresses by navigating platform game puzzles and shooting enemies with the equipped weapon. When the player collects multiple weapons, they may be toggled at any time with the press of a button. Defeating enemies sometimes yields yellow triangular objects, which give experience points to weapons when collected. Weapons may be improved up to level three, but taking damage causes weapons to lose experience and levels. Health and missile capacity upgrades are scattered throughout the game world. The player must interact with a variety of non-player characters and objects to complete the game.