Blue crystals: It is possible, but of course hard

There are those spikes and the icy, sliding ground... I would rather miss a few points than lose a life there (which can be worth a lot more)
I think I beat Tuber in my 3rd try... Not sure. Most of his attacks are easy to dodge once you know how they work, so in the end he is not more difficult than level 90, and far easier than 94 or 95
