The aesthetics, the sound design, and gameplay all works really nicely together. Using the colourful tiles was an inspired idea.
I enjoyed being able to rotate the piece, although it felt a little slow. Maybe you could make the scroll wheel also rotate the piece in either direction at a faster rate. A bit unconventional, but I think it would work really nicely.
I encountered a few game breaking bugs when changing tabs or scrolling down the page, but I'm sure you're aware of that by now.
My game also has a block merging game mode (added after the jam deadline) but it's very different and not very challenging because of trying to make it coherent with the main game modes. Love that someone else attempted it and put in the effort to make it good.
Well done, fantastic work!