We are getting some questions about more on the gameplay and how the will light mechanic work.
First, I went into a little more detail on why we dont show a ton of gameplay in the comments. But there is some gameplay in the main video.
The world is full of lost souls that are trapped (Ghost lights). Knite is a ghost piper (explained more on the main KS page and mistlandwiki.com ). While the game is an action adventure, the gameplay is deeply based on exploaration (along the lines of a Metroid or Castlevania).
Learning new songs and interacting with new lights serves as your "upgrade system". However we arent upgrading a weapon system we are upgrading his ability to interact with different types of lost souls and even control them. Learning a new song will help him interact with differnt types of ghost lights and in turn help discover new things.