OK, here it is: the infamous level of 9-7.
I do have to say that this is probably the most difficult level of the game. However, it can be beaten with concentration, timing, and memorization.
A real challenge is beating this level and collecting all three Star Coins in one run. I tried, but I couldn't do it. I did get the first and third Coins in one run though, but it seems hard picking up that second one and escaping before all of the ice melts away.
Anyway, there's one more level left in World 9, and it's the last level of the game and of my single-player playthrough.