This barrier looked like it would require 4 blue hearts, which I only have a couple of so far... but I guess any hearts will do.
This is a really interesting way of changing up the mechanics enough to justify another level. Now you no longer get your dashes recharged just be landing on the ground. You only get your 2 dashes recharged when you collect a diamond or move to a new screen. There's a lot of really cool looking heart themed imagery in the backgrounds, including some realistic looking hearts. This level also introduces these block platforms that are kinda like the pink cloud platforms that can fling you in a direction before disappearing, except with these you can cling to the sides of them too, as well as conveyor belt walls and big fireballs moving around in a pattern.
Another thing this level introduces is a switch that turns the world blue. When the world is blue, lava goes away, and fireballs into blue things you can bounce off of (but they still kill you if you touch them from the side or bottom), and makes them move around much more slowly. Then when you hit the red switches everything turns back to the normal lava mode. Also when the world is blue, those flinging platforms don't fling you, instead they just slowly sink and disappear.
Later, there's a layer of lava chasing you from the bottom (or cold water when the world is blue I guess). This doesn't really do much to add to the challenge, it's just that instead of falling safely to the bottom and starting over again, you fall into the lava and die and start over again, as long as you don't dawdle the lava is never really a problem.
Then it goes to a SMW style layer 2 gimmick where there's a lava layer both above and beneath you, and the red/blue switches change the direction of these lava layers from moving up or down, in addition to the other effects. That big room where you use gold feathers was my favorite section.
The last part of the level is a B-side tape room with beat blocks mixed in with the level's giimmicks... then there's just a comfy dream land area where you fall forever and collect a blue heart.
That 8th level wasn't as hard as I was expecting. You just need to preserve your dashes a lot more than usual. But the fact that this level has a B-side makes me excited.