took the unpaid take-home down to two hours instead of the suggested six and got the offer anyway

The assignment said 'take as much time as you need' which I now know is a trap. I capped myself at two hours, shipped something smaller but clean with a note explaining what I'd add with more time. They said the note mattered more than a finished feature would have. Setting your own boundary on these things doesn't seem to hurt as much as I feared.