I wasn't sure what I thought of this game (besides loving the aesthetic!), but then I came to the comments, and saw that the portal was meant to be something you figured out. I went back to the game, and had a great time!
Thanks for trying my game and giving it a second chance! My idea was that the player discovers the use of the portals through the gameplay but surely I will have to document it better in the next version =) Thanks again for your words!