Spectacular visuals and style. I also really like this idea and love how it works.
I think working on controls / usability would be the next step, aside from obstacles / different levels.
Controls-wise, I had some difficulty moving through the menu on the web version, had to click around a lot just to scroll through options. Also, when placing items, sometimes it would say no, unless I pulled it away for a sec and put it back, then it worked. Edge case stuff just might need some slight tuning on that part.
I kinda didn't understand how much each piece would contribute to wash and cool factor, so I kinda just had to throw a lot together and hope for the best. I sorta got it eventually and built up a meta. But some slight indicators may help for difficulty's sake. Unless you want to let players just trial and error it, which is a fine choice too.
It's really cool how you built this in 4 days. That's incredible for how well it looks and is put together. Great job. One of my favourites of the jam