As far as I can tell this level is not solvable,
Do you test your levels
A rule to follow when posting levels, "If you can't solve it, Don't post it until you can"
Too true, Kiki!
I've looked into the editor to see what's the problem and found out that:
1) It's a wooden box generator and two boxes are in the walls.
2) Even then, there is nothing to open other gates to get the rest of the rainbow coins. (which would open the white gate)
Rest in peace, Kym. I hardly knew ya. Rest in peace, Marinus. A bright star, you were ahead of me on my own tracks of thought. I miss you.