... I suppose this couldn't be strictly called a "Playground". ...Hmm. I suppose it did have 2 specific goals, and one relied on the other. That's probably why I liked it so much. I knew what I wanted to do and I knew when I was finished. So you're right, it's not a pure playground level. Still, it's a great variation on the concept. There are many fun things to see and I was free to wander in any direction as I pursued the goals.
Spoiler: About that special area (click to show/hide)