The playground was the inspiration for the post. I always wanted to be able to fiddle with malloc implementations and see how they work in this way.
Admittedly the playground is hard to understand at first, and a touch janky in places. But the workloads are taken from for-real malloc/free traces on programs!
When you think that I (and probably the vast majority of developers) used a pen and a paper for the first few years every time I tried to visualize more complex memory, then that's a big upgrade.
Especially because you can scroll through all the steps.
How I wish I had something like that when I first learned C.