mobile submenu

Hello!

My question is hypothetical as in I haven’t done anything yet:
So my website seems to recognize not only screensize but also mobile devices
and submenus behave differently on mobile. I found this code in the original css:

.main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true {
  display: table;
  margin-top: 0;
  opacity: 1;
  padding-left: 0;
  /* Mobile position */
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  position: fixed;
  z-index: 100000;
  /* Make sure appears above mobile admin bar */
  width: 100vw;
  height: 100vh;
  max-width: 100vw;
  transform: translateX(100%);
  animation: slide_in_right 0.3s forwards;
  /* Prevent menu from being blocked by admin bar */
}

it describes what happens but I can’t figure out which css command commands this behaviour only on mobile devices.
In looking that up I found that it’s possible with a media query for “handheld” but I didn’t find that in the code…

So my question: How can I change the mobile behaviour?

Thanks, Alex

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