How to use flex to allocate elements in a row to maintain two elements [duplicate]

Question

I want my elements to be in the middle of the screen and arranged vertically when on the mobile phone, but when switching to the tablet, the screen I hope to present is two elements in a row, presented from left to right!

Attached is the schematic diagram, but I'm stuck and don't know how to implement such a layout.

ul {
  display: flex;
  flex-direction: column;
  align-items: center;
}

@media (min-width: 768px) {
  ul {
    flex-direction: row;
  }
}

<ul>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
</ul>

Answer 1

You can try something like this. Essentially just make two different ul's then nest it in a wrapper. Then you can tell the browser to switch to flex-column for phones. Resize the browser to see the effect.

ul {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 0;
}

.wrapper {
  display: flex;
  justify-content: center;
}

/* change to column for phones */
@media only screen and (max-width: 600px) {
  .wrapper {
    flex-direction: column;
  }
}

<div class="wrapper">
<ul>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
</ul>
<ul>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
</ul>
</div>

Answer 2

Is this what you are looking for?

ul {
  display: flex;
  flex-direction: column;
  align-items: center;
}

@media (min-width: 768px) {
  ul {
    flex-direction: row;
    flex-wrap:wrap
  }
  li {
    min-width:50%
}

<ul>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
  <li>title</li>
</ul>