Very awesome game! I'm surprised that you're able to put together such a high-quality demo although it's "unfinished". The graphics, visual effects, UI and game play are definitely all there - if you had some music going on (which I think you don't at the moment) I'd totally believe that it's a game I can purchase on a big platform.
Some more detailed feedback:
- Some parts of the game feels a bit slow. I think this is the most obvious when the level starts and the enemies are spawning in, and when the player waits for the next wave. Consistent and fast collection of the sparkles would be really helpful as well, at some point I thought I was supposed to collect the sparkles by clicking them myself because they started to pile up on screen until they started flying to top left corner by themselves. It might be my computer's lag as well, though.
- I wasn't sure what I was supposed to do in the level up screen, but I did figure out some thing that allows the game to proceed. I understand that this might the thinky part of the game and it looks so cool, but I needed to pause and do a little trail-and-error.
- speaking about pause, it'd be more intuitive if the player can pause the game at any point as well as to speed things up. If the lack of these functions is by design, however, go with what you have in mind.
- For the level up screen's UI, The bottom screen has a purchasable item hub and the tab on the left says "store", which makes sense to me. However you also have a "sell" tab on the right, and it makes me think that I can click on it to switch the store hub to the sell hub, which is not the case. The action I made to trigger "sell" is to drag a purchasable item on screen and then drag it to sell. I think changing the UI layout might make it more intuitive, something like a sell button / area on the right side of the screen that's not touching the hub at the bottom.
That's it for now, lmk if you want me to specify anything I said! Really great work and I can't wait for the update!