In the game, there is special rainbow levels you can unlock to play, the way to unlock them is by touching the flag pole when the 2 last digits of the timer are the same as the world number! The 3 special worlds do not have a world number, but they are referred to as 7M 8F 9S! Once you complete that task, he arrow where you spawn when you first click a world will turn into a rainbow, play the level to get mass amounts of coins in little time (and if you get all the red coins, you get a golden flower in the reserve slot!)

note: the level ends once you fall off the screen

note: after falling off the screen, you will go back to the world, and have to complete the task to unlock it again

note: each rainbow level is unique, and sometimes will have the same theme as the world it is in!

what does this have to do with speedrunning?

^

I mean, it's useful to know the firework time thingy but rainbow levels are pretty useless