Advanced Level 9: "Three-Fold Maze"

Here is a summary of the Mark Frohnmayer route, as shown in the gameplay demo in the older PC version of Marble Blast:

You need to go up the ramp to the left of the start, changing gravity as you do so, and then down a couple of ramps to the right to the first gem.

Now fall off of the the platform on the right hand side and drop down to the long platform below (watch out for the stripey block in between the tow platforms). Travel down to the end of the platform and grab the gravity switcher, continue one and grab the gem, then go quickly up the ramp on the left hand side, grab the gravity modifier on the right to fall onto the wall, then turn directly around.

Cross the long ramps quickly by leaping off the top of the downward slope and bouncing up from the bottom. This should get you enough height and momentum zip neatly up to the top of the upward slope.

Now comes the hard part - quickly travel diagonally to the right and leap toward the crossing ramps. Your goal here is to hit the nearer of the two gravity modifiers on the downward sloping ramp, while keeping enough momentum to roll up the ramp as gravity switches. The final gem is at the top of the ramp (formerly the bottom of the ramp prior to the gravity switch)

You can then drop down to the end pad, which will be directly ahead of you and below (careful not to hit the gravity switcher beside it)

Good luck :)