The art style on this is very cute! Though, the camera is very zoomed out, and it makes it hard to read the details on the player character. It makes it look out of place-- for a sprite that size, the outlines should have probably been thicker, or there should have been some other way to make it easier to read from a distance.
As for the gameplay, it's a fun idea! It's cool to look for the gems and bones underground. It seems like the digging is supposed to be the main mechanic, but a lot of the other features don't mesh with that. Like, I'd prefer if the combat had something to do with the digging, instead of a completely seperate mechanic, or if the enemies were effected by gravity, and you could sort of corral them where you wanted to go by digging out pathways. I get that you needed to fit the summoning in somewhere, but you could have made that work with the digging as well-- imagine you have to dig pathways to get as many enemies to one area as possible, so that you can summon and kill them all at once, getting a big combo.
I conceptually like how picking up gems slows you down, and the idea of it being easy to go down and get them, but slower and harder to bring them back up. In execution, though, it ends up slowing down the gameplay too much. You might want to change it up to do something else, like... rebalancing it so that you just don't get digging on the way back up, since the slow movement can be frustrating. I also worry you can softlock yourself by just digging everything out.
The presentation is very nice, and I like the ideas! The biggest thing I'd focus on for improvement would just be making all the mechanics mesh together and feel like cohesive parts of a whole.