Sorry for the late reply. I've been busy with a lot of things. I will probably come back to this (or make another project) once Winter or next year comes around.
I actually started working on a small update, but for now I just tweaked the balancing of the game (so it's easier) by buffing towers (yes I already buffed the sniper) and nerfing enemy spawn rates. I also added some upgrade and sell buttons for mobile compatibility, and made some of the ground towers more useful (I won't spoil what I did though). If I will have more time, I really want to add tier 4 upgrades to towers, maybe 1-2 new towers (probably returning ones from the old scratch game) and 2 new enemy types which I already have planned out. If I don't have motivation or time I will postpone these changes to the winter update, but I will release the small changes and features I have already added.