Q: Does the total effect of playing a card have to be resolved before checking for win conditions, or could someone win partway through?

There are a lot of cards where, unless all steps are considered to be simultaneous, there could be timing issues.

A: As a matter of fact, yes, in Fluxx all consequences of a card play are considered to be functionally simultaneous, so there are a lot fewer timing issues than people sometimes think.

A good rule of thumb is that things in Fluxx (and many other Looney Labs games) are considered to happen simultaneously, so if there are timing issues, assume that things take place all at once, and then consider the outcome.

See also: We think we broke the game…