I see a lot of people talking about this, but no correct answers. To achieve this responsive layout, where box4 tucks up under box2 instead of aligning with the top of box 3:
<div id="container">
<div id="box1">1</div>
<div id="box2">2</div>
<div id="box3">3</div>
<div id="box4">4</div>
</div>
Multi-column layout insists on putting boxes 1 and 2 in the first column and 3 and 4 in the second column, instead of the preferred order (as in Jhey Tompkins' often-linked Medium post); and
Flex insists on aligning box4 with the top of box3.
So neither one works. I'm pretty sure this isn't impossible. What's the strategy?