We are so busy this holiday and we cannot make any progress for our game.
Anyway, we managed to continue this and this is the concept art for our level:
Looking good, eh? But I don't know if I can 'turn' that into code.
Meanwhile, I've coded a little bit and achieve this:
Utilized Tiled as the editor for the map and for generating box2d fixtures.
And I managed to create that track indicator thing on the top of the screen.
These assets are temporary (especially that pink motorbike thing).