I've been working on Game Design Documents for a while but I need the opinions of others to improve. Can anyone critique the game design document I've attached and give me feedback on it?

About the game in the document:
The game is a casual game where the player would use their mouse to cause a falling sphere to explode into fireworks for points.

No offence, but what you have there is not even a design treatment, let alone a GDD. I've seen longer one-pagers, for God's sake!

First of all, add your name and the document's version on the cover. Next, if you have a table of contents with numbered pages, put the numbers on the pages, too. It may be a PDF for now, but when it's printed, people don't count the pages to see which is the current one.

Don't just add a sentence to each, um, category. A game designer's job is to write. So you do that. Add as many details as possible: all of them, that is. You see, a GDD is not necessarily a technical document. It describes everything the gamer will see and do in the game, in a manner that allows everyone to understand it.

I'd say more, but I'm running late. Good luck!

Where's the design document? All I see is a template.

Since the game was simple I was trying to keep the design document simple as well.
I'll start improving on it.