Thank you for sharing your opinion!
Is the key assignment the problem with the controls, or is moving the character too complicated?
I originally planned the control from the keyboard with [z, x, c] and [arrow keys]. (Inspired by Hollow Knight). Then I realized that some keyboard types have [y] or [w] instead of the [z] key. That's why I do several key assignments. (Controller is also supported.) But it might confuse the player.
This will be solved if the keys can be modified within the game.
The empty areas are because of the loading gates, because I did dynamic level loading. Instead of empty backgrounds, I'll come up with something else. I will improve myself in this.
I will check your game too!