You may be tempted to shout out "Where's the glitch?"
But trust me, there are no glitches on the menu today.

First gather all eight bonus coins.
Now push the east sticky cube up so that is joins with the north cube.
Get the rainbow coin, and slide the west cube left and down until it sticks to the lower-left wall.
Go back up and slide the south cube right and down until it sticks to the lower-right wall.
Go back up and push the right metal box into the lava.
Circle clockwise to the last metal box on the left side.
Pushing this box into the lava will trigger a metal brige to appear north just above the exit.
Push the box into the lava, and without hesitation, go clockwise to cross the bridge and exit.
An alternate way is to slide the left metal box up one square and then push into the lava. This will make the route one tile shorter.