Hmm, try 640 x 360. That might account for the way Itch scales the display. I’m not sure how the mobile control interface is added to that, though….
What website are you embedding it in, if I may ask?
I tried 640x360, though, it was still the same... I tried tweaking the other options too if that would work, but same result. After some searching on other games that's playable in browser (and also made in GB Studio, not GB Studio 2), I noticed that it was the same case for me. I think that maybe my version of GB Studio isn't compatible with the landscape orientation for my mobile phone (screen size is 360 W and 640 H). I think I'll just leave it at that state, I can still play it on my phone with an emulator + ROM after all.
As for embedding, I set it to "Embed in page" to manually set the size of my game, instead of clicking to fullscreen.
Thank you once again for your help and replies. And also sorry for this StackOverflow-like comment. I'll just leave the options as it is 😃
Here is the link to the prototype: https://armanlone-main.itch.io/untitled-jrpg.