Other people have been saying this but I definitely agree with the inertia that others have pointed out definitely doesn't fit the game. I get that is probably trying to imitate the sonic aspects of the game but I kind of feel like if you want to go that route the levels may need to be a bit less maze like which would kind of alienate the metroidvania aspects you are trying to accomplish.
The attacking animation might need some work as I feel like it is visually weak. I know the DS castlevania games do a great job at giving weight to the heavy weapon and fast crispness to the lighter weapons. Try playing through Order of Ecclesia and look at how sharp and quick the animation of the sword is or how heavy some of the hammers feel depending on how you want your character to feel.
One this I really like though was the directional up and down modifiers to your moves. Pressing up and attacking to get a little bit of height was a really interesting move that while small helped add to the depth of the game. Sliding I felt might have been a little too fast but the thought is good.
The mechanics seem pretty solid and intuitive although I feel as if these points can be improved upon.
1. The shovel attacking animation and dynamite explosion should probably have some sort of animation on the portrait of the defending character to sell the fact that they are getting damaged.
2. The Shovel buy icon doesn't seem to change much in color when it is available.
3. The auto buy option should be toggle-able within the combat screens.