Thank you very much for the comment!
Try going through the tutorial again carefully — it takes about a minute.
Green light shows the way, reveals healing lights, and opens hidden paths.
White light slows down enemies and helps you avoid danger.
Purple light reveals hidden texts needed to complete the level.
Your current objective is shown in the top-left corner.
And by the way, make sure to reach the end — there’s a good ending and an explanation of the game’s true meaning :)