I would honestly buy this on mobile if it where fully developed. There are three things that I think would improve the game.
1 - The knight needs some sort of invincibility after getting hit by an enemy, I went very far on 3 hearts but was then cornered by quite a few enemies and then bam all hearts gone at once.
2 - Your environment should change as well, if the player gets far enough, rewarding them with a new environment like a cobblestone section of the dungeon for example, would help make it not only better visually but help the addiction factor of the game.
3 - Rewarding the player for encounters, if you where to give coins for a defeated enemy and then allowed you to teleport items that can be purchased from a store to in front of the knight it would improve the game. Even having a random chest or item drop tied to specific enemies or bosses would help with making the encounters worth it.