The recent update implemented "Fearless Cave". It basically adds another difficulty to the Misty Cave. In order to access it you must complete all 10 levels of Misty Cave and then you can choose to do Misty Cave.
I've been working on the Misty Cave calculations. Sorry it's going so slowly guys! Unfortunately I'm limited on the number of times I can actually do the cave levels and I'm testing each cave level with each level of upgrades. The good news on that is that there will be a much more comprehensive guide because of the method I'm testing.
Anyway that's it for now. Thanks for visiting guys!