How do you block knytts and fluff from running on air?

You know when you put an animal that walks on the ground and it'll walk right into the air, well I always just use something like grass and just make it [3] so that it becomes a barrier. But it looks weird when juni gets stuck on a piece of grass. Is there any other way to block them in?

Sorry if this is confusing

I don't think there is any way to block them.

It's not confusing, I've come across that too. If the animal and place they're on/in is purely decorative, distributing invisible blocks does the trick. You can also try and select some specific element of your tileset that fits well; a larger piece of grass, a corner -- when I tried to build screens that included walking creatures in the air, I was using a tile that was just a small, small solid triangle on the corner of the tilespace, it looked alright. If you want, you can post a screenshot and ask for more specific solutions.

oh okay thanks. I was just making sure I wasn't missing out on some super animal blocker thing.

I recall a way to solve this problem was to make a tile small enough for Juni to pass it but high enough to block walking sprites. Unfortunately I don't remember exactly how high you need to make it; perhaps 2 pixels. Painting it with an almost transparent colour also makes it basically invisible.

I recall a way to solve this problem was to make a tile small enough for Juni to pass it but high enough to block walking sprites. Unfortunately I don't remember exactly how high you need to make it; perhaps 2 pixels. Painting it with an almost transparent colour also makes it basically invisible.

I think 1 pixel does the trick.
In the past, I've used layer 2 areas that they can walk onto, that juni avoids contact with. This may not always work out visually, though..

I'm pretty sure it's two pixels.  I remember I tried one pixel and it only worked about half the time.

2 pixels is enough, but 2 pixels is also enough to stop Juni.

It really is the best way to design your level in such way that its obvious.

You could draw a fence so its obvious that creatures will not pass it, or like many people do, place them in a valley/gap in the bottom which can be just one row lower.

2 pixels doesn't stop Juni - it was something I had to work out for my current level. She can't go up three, though.
The easiest way is probably to put your fluff in places without edges to walk off, though a tiny blocking thing is viable if you're making your own tilesets.