The game download includes a manual. For more info, the creator has also made a guide on his site:
www.remargames.se/gameguides/i...

How you play will determine Iji's mentality and, ultimately, what ending you reach.

Will she simply try to survive at any cost?
Will she become an avatar of retribution?
Or will she seek peace without bloodshed?

In this 2D action-adventure platformer, you are Iji, a young woman having a very bad day. She awakens to a newly cybernetic body, a shattered Earth, and a mission: get rid of the alien invaders, one way or another.

I want to tell you about one of my favorite games of all time: Iji, created by @remargames.se / Daniel Remar.

Get it for free from his website:
www.remargames.se/iji.php

(He has many more free Windows games there, too. You might know him already from games like Hero Core or Princess Remedy.)