I completed the game, and now the blob of non-matter is sleeping soundly... didn't it forget about Polwan, though?
I won't dwell over jump delay and lack of audio, as I'm sure you already heard about it plenty of times. One thing I wonder about is whether elemental input could be simplified somewhat. One idea would be using the same key to apply elements, just picking whichever is applicable at themoment. But of course it would cause trouble with overlapping element-dependent items.
One idea that comes to mind is using approach like in Fury of the Furries, where - if you stood still on the ground - you could enter ability switching mode and then exit with whatever ability you need at the moment. Then you could make the player use the ability freely (rather than at the designated spots) and have them figure out what works where. Of course, it'd likely require redesigning gameplay elements, though it may be for the better; the current objects were mostly "railroady" in their use, even the multi-element ones like cauldrons.
I think the game does a good job presenting its setting; the story in description is one thing, but also I saw all these posters/graffitis and such. I think focusing on the setting and storytelling as well as making creative bosses themed after specific kinds of alchemy could work really well for this game.
Overall, I enjoyed the demo, though I feel the gameplay elements and/or level design could be reworked to allow a greater variety of interactions (rather than boiling down to "I see wind, I use air, I see pipe, I use water, I see wood, I use fire").
