How do you maximize moonwalk distance? Is it based on input speed or the shape of the movement? Both? Something else entirely? Super curious about this because I want to start applying to to my game a lot more.
The amount of speed you gain from moonwalk depends mostly on your control stick position on each frame, since that's what determines your acceleration. The most important part is probably to move your stick to somewhat backward position ASAP after initiating dash, since on any frame beyond first where you hold forward you'll accelerate in opposite direction of where you want to go.
Optimal method for moonwalking right is something like this: 1.
(dash input) into 2.
(best possible backward acceleration input for frames 2,3 of dash), then roll to 3.
.
Full half-circle is bad because then you'll end up holding forward for unnecessarily long time. Instead you want to smash your stick directly at the opposite downwards diagonal notch first(or little below it to make sure you don't accidentally dash or turn), then roll to full backward input from there.
Avoiding middle with the stick isn't actually that relevant, what you need to do is to first move your stick backwards but not all the way. Holding the stick a bit backward for 2 frames disables smash input window for turn and makes you unable to dash back anymore. It works the same way like spotdodge with control stick for example: You can't spotdodge if you first hold slightly down for a bit before the full down input. The diagonal corner notches are convenient for moonwalking, since they'll stop your stick at backwards position that gives backward acceleration but barely won't cause you to dash back.
With falcon, your speed before the moonwalk affects the result a bit. You'll get slightly further with moonwalk out of walk or dash. It's also notably easier to move your stick to back quickly when dashing backwards, because when you dash back, you'll actually turn for 1 frame, which kind of removes one frame of acceleration forward.