( a momth ago) Like Tilu, I'm stuck 2 off, too. For a looong time. Giving stars, now and hoping I'll find the cut! :)
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EDIT 2023, 17th April - I can't believe I finally solved this. 72 is extremely tricky, IMO.
I was baffled at first. How can anything be faster than 80? But then after several minutes of seeing how this puzzle actually works, I got it! Wonderful solution and design!