Thank you for the review!
I didn't have time to add the polish and music because I wanted to prioritise good puzzles. I've definitely been thinking about how to introduce the emotions and make them visually and audibly unique.
I designed the levels to make the player believe you have to bump into the altars initially, the ability to activate them by sliding past is actually a bug turned feature I introduce intentionally with one of the levels and it's one of the key "tricks" to solving a few levels. Now that you mention it, I will look into visually and audibly differentiating between bumping into activation and sliding past activation.
My take on alchemy was pretty abstract, seeing it as transition from one state to another, that's one of the core mechanics in this game, changing from one color (emotion) to another. The shadow thing is part of the story/setting which I didn't have time to create cut scenes for. One again, my take is pretty abstract, shadows are the absence of light, but I take it to be an absence of *something*, with a certain darkness to it, so evil spirits (which I represent by being a black color) are souls with an absence of emotion, hence they are able to go into voids which would otherwise kill you.