The winning attack I meant to do would have worked.

But because I didn't know if there'd be enough time on its fuse to make it the required distance, I went over to collect the other crate just in case. Then I didn't take the chance of aiming the crosshair down 1 notch from straight up with the view of the crosshair being cropped by the roof, because tapping the Down arrow quickly enough to do that sometimes is ignored and sometimes isn't, due to the way WA polls its keyboard input. But if that aiming is done in advance, there's plenty of time to do it: