2D Platformer Tutorial

I think that you're headed in the right direction with your modifications, but I have a few clarifying questions:

1. What do you plan to do with your levels? How will you make them unique and significantly different? The best advice that I can give you in terms of level design would be to make sure that each level has some sort of unique identifier. New types of challenges, enemies, obstacles, or powerups can massively help with this. Putting some time into playtesting and differentiating your levels (to figure out, from a player's perspective, how the level plays) can also give you some direction in how to design things.
2. What do you mean by element, and how do you plan to implement this?
3. What new ability or item are you planning on adding, and how will it affect gameplay?

Good luck!