The art is super cute and the puzzles are great so far! (Except level ÷. I had to decompile the game to find out that that you can possess the lifeless avatars by clicking them. With that information, the puzzle was fun, but that really needs to be communicated, haha.)
But, yeah, to echo what You're the They/Them Now Dog said, the UI/UX could use a little tuning. On top of what they've said though, adding music/sound effects would really elevate the experience of playing this game! There are a lot of well made and free to use options on OpenGameArt. (If you'd like some recommendations, I can definitely find some tracks for you!) Alternatively, you can create some great results by clicking around on Beepbox.co.
Outside of music, the only sound effects I can think to add would be for movement (possibly with an altered version for rewinding) and for dialog.
Oh, one more thing: I'm not sure if this is intentional, but some puzzles use elements before they're explained.(I ran into this with the XOR blocks, the goop blocks, and the... dead bodies? I still don't know what they're supposed to be, haha.)