Are there any B-tree programs or sites that show visually how a B-tree works

Question

I found this website that lets you insert and delete items from a B-tree and shows you visually what the B-tree looks like:

java b-tree

I'm looking for another website or program similar to this. This site does not allow you to specify a B-tree of order 4 (4 pointers and 3 elements), it only lets you specify B-trees with an even number of elements. Also, if possible, I'd like to be able to insert letters instead of numbers.

I think I actually found a different site but that was a while ago and can't find it anymore.

Answer 1

Found one here, but it's not the same one I found before. I wonder if there are any others?

b-tree simulation