Really fun and addictive, and I like the upgrades, the chains that the bombs make are really cool and the sounds are really satisfying.
But there are some problems, like sometimes the player just starts floating, when you move to a empty space, which removes some fun, it definitely makes the game easier, but less fun in my opinion.
Then you handled the pixel size in the map really well, but the UI has the pixels scaled so incorrectly, some pixels in the UI are really small and some too big, so that should be fixed, as that just look bad, so you probably knew that already, but Im still saying it: PLEASE HAVE SAME PIXEL SIZE FOR ALL PIXELS, so never scale pixel art, draw new art, always, scaling it always will look bad, even in UI.
Also post processing, please add that, bloom and vignette, and tadaaa, the game magically looks 3x better, do that.
Also there's way too little feedback for taking damage, add some camera shake, particles and maybe a red flash of the screen, it's hard to realize that you took damage, and that's really bad.
Then the ghost and spike thingy, the ghost should have death particles / damage player particles and the spike should get destroyed when you touch it and have particles too, because now you just end up standing on the spikes which looks really weird.
Then for the gameplay, the game is way too grindy, at the end you end up just spamming down to get money and not really caring, deeper down you go, there should be better coins, so it's less grindy and you don't end up just pretty much spamming. And the 50k coins achiement, WHY? I ended up just autoclicking down arrow key to get that for like 4 minutes to get that, like how should you get that without an autoclicker, im not gonna spend a hour just playing this to get that.
Also I don't know if there's some cool lore that I missed as that "how does this with the theme" box kinda suggests that, because I didn't get 1000 meters down, only 900 and then I quit, so if there's something cool I missed, sorry.