Hello,
In my case i can subjectively feel larger intervals, like P12, M9... but my reflexion is just oh it's a fifth, but an octave higher/lower. Maybe not the best reflexion to have to feel and hear intervals, but in my case it does the jobs pretty well !
For being better with the largest intervals, focus yourself on the intervals within an octave.
If you already recognize easily these ones, it'll come very fast (it worked like that in my case).

Sorry if i did a few mistakes, english is not my native language :)

What I found is that at first I was just feeling for the largest interval, but as other games reinforced my interval recognition, I started to better recognize what the intervals actually were, at least inasmuch as the other games have been covering the interval. For instance, I haven't yet gotten to the the levels of the interval recognition games where they mix in 6ths and 7ths, so there my recognition is a lot more fuzzy.

It's a good example of how the various games reinforce each other and come at basic skills from different angles.

Thank you for your answers @Cédric DRAI and @Victor Wilburn . It's very helpful to read how others approach it.

Pas de problème Cèdric, moi aussi je suis Français et je trouve tu t'exprimes très bien en Anglais. :)

For me, in the beginning I felt intervals I couldn't recognize yet and their distance, but like others said as I learned the intervals, I could just identify them. Sometimes, then I could only identify ascending ones, but then would try to feel how far apart for when it is descending. As you progress, you'll have a mix of ones you can identify and ones you still feel. In retrospect it is an interesting and useful exercise because if forces you to develop the ability to listen before you can identify the interval. I can't yet identify all of them, so I have more to learn.

If I'm being lazy I'll try to listen to them all quickly and try to intuitively feel which one seems bigger. This has worked less for me as the levels have gotten harder, though.

If I want to make sure I beat the level, I attempt to identify each interval by name before making a selection.

For me the hardest part is to tell the difference of the same intervals when adding octaves. Somehow my ear thinks that a major third and a major tenth sound the same, but a difference of half a tone up or down changes it completely and I rarely mix them.

Thank you @Ken Matsuda @Paul Cox and @Riv Kah . So interesting to see how differently we all go about it.

@Ken Matsuda I like that you can feel before you can identify. For some reason I'm the other way around...

@Paul Cox I do the same when I want / need to go fast and feel it out. I wish I had @Ken Matsuda 's skills to get the results as my success rate drops considerably, like you, when I do so.

@Riv Kah those higher octaves are hard indeed. Two things that have helped me with them: listen for timbre (particularly the presence of lower harmonics) and trying to match the interval singing with a focus on the fundamental of each note.