The game ramped up in difficulty quickly; the game design is solid, and the graphics are simple out of necessity. I don't know how this gameplay matches your explanation of the theme.
What does a little flame going through mazes of lava and dashing through metal have to do with "Diving Deeper"? You can't say it's because it's an allegory that means every platformer puzzle game ever means the same thing.
Overall, the game is a solid platformer foundation. The music got a bit repetitive.
Overall, you did a great job making a game that feels and plays solid.