Interesting. Mouse support is definitely something I might put into the controls menu when I get that feeling how I want it to, the vertical line is an easy add, so I'll start on that. As for the combo chains, currently they are only indicated with the merge sound effects. I definitely want to get a visual indicator going on that, but just haven't gotten around to it yet. The scoring and death plane both worked fine when I just now played this web version, so it seems like that might be a linux/steam deck thing, as I have had very little testing in that area. If it is still non-functional on your desktop, please let me know. I'll look into seeing how viable a linux web export is, or I might make a Linux download if that makes the game file too large.
Anyways, means a whole lot to me that you wrote this, lmk what pokemon I should add(although they might not be added for a few days, as I have once again jumped into an idea that I have to learn how to implement)