You might remember a few months ago a game called Qui'Ifon (developer: ultim8p00) was posted about, which had some similarities to Cave Story. Since then, the engine has been reworked, its name has changed to The Undertaking and a new demo has been released, although apparently it was a rushed release so expect some bugs.

Author's description: "It's basically Cave Story meets swords meets Knytt (or Seiklus)." However, he also goes on to say that he wants to distance it from Cave Story.