Cave Story is an adventure platform game done by Studio Pixel in 2004. You wake up in a cave with no memory and find a village populated by Mimigas. They are being persecuted by the Doctor, who is looking for Sue Sakamoto, a girl who had been transformed into a Mimiga.
The whole game has been developed over five years by Daisuke “Pixel” Amaya in his spare time. Initially done for Microsoft Windows, it has been ported to several platforms.