wow! That level gave me some work. I found it very interesting.
Unlike Hi19 experience, my 2 off was the right path and needed just a very simple optimization. So probably it means that there are several 2 offs. Glad I got one only.
Nope, can't improve on 2off.
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Edit: A month later, still 2off, so I tried something new and finally got the trick . 5 stars for difficulty.
It's beaten me so far, no better than 4 off.
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Edit: Finally got it, I'd been moving the boxes in the wrong order all this time, the correct solution seems very unintuitive to me.