I'd like to create a Feynman diagram for the λφ⁴ theory that is simply the interaction 4-point vertex. For some reason, in TikZ-Feynman it seems to be automatic that the incoming and outgoing lines go up-down and left-right even though no one would ever draw it like that. Short of manually inputting the vertex locations, how can I get this rotated 45 degrees?
(I've seen a similar post here, but it seems like that person wanted the lines positioned in a strange way. I'd like them positioned at 90 degrees to each other.)