How do I open the door on the first slime forest level?

Question

I picked up Wizorb and I have to say it's a cute game. I've made it to the second world, the slime forest, and the very first level has a door at the top with some sort of glyph under it:

I imagine that the glyph is some sort of hint as to how I am supposed to open the door, but it eludes me. What am I supposed to do in order to get this door to open?

Answer 1

It seems that the door can only be opened once all levels of the Slime Forest are complete. The world's boss drops a blue quarter-circle with an identical glyph upon defeat, which allows you to open the door on a second playthough of the Slime Forest.