Boy has this taken me weeks. I have just managed to complete it after finally getting the yellow Vega (I put him up to Level 5) with the downwards arrow. I also used Edward, Temper, Bob and Whisper. First I collected the yellows to get the down arrow and destroyed one gate (right hand side) then I used the green sideways arrow to clear the last line of black blocks but I didn't use this until I had a purple '9 block bomb' at the ready to clear 2 gates at once. So as soon as I cleared that last row I was lucky enough to have the purple one in place ready to go! You need to be prepared with them all in place or the black blocks will take over again. Hope that is understandable :-)