HTML + CSS: Нумерованный список с числами внутри кругов

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I can't for the life of me figure out how to do this. I've tried using list-image but then the numerals don't appear. I tried setting a background, but it won't appear behind the number if list-style-position is set to outside. I tried setting it with a background and list-style-position: inside, then putting the text inside the li in a div to align it, but no combination of floats, margins, etc worked without wrapping around the numeral.

This seems like something I've seen on plenty of web sites, but at the moment I can't seem to find a working example, nor is Googling for this giving me any results.

So, can anyone help me with this? How would you create the above using HTML+CSS, ideally without using JS, and definitely without using just images. This text needs to be selectable and copy/pasteable.

Because a commenter asked, here's the markup I have right now:

<ol>
  <li><span>List item one.</span></li>
  <li><span>List item two.</span></li>
  <li><span>List item three.</span></li>
</ol>

None of the CSS I've tried has even come close to working, so I'm not sure the value of sharing what I have currently. Here's one version that failed...

ol { display: block; list-style: decimal outside url('/images/lists/yellow-circle-18px.png'); }
ol li { width: 176px; margin-right: 20px; float: left; }
ol li span { display: block; }