inline-block
leaves white-space between elements.
To remove this space, write elements on same line.
Change
<ul>
<li>Semantic Cell 1</li>
<li>Semantic Cell 2</li>
<li>Semantic Cell 3</li>
<li>Pretty Cell 4</li><li>Pretty Cell 5</li><li>Pretty Cell 6</li>
</ul>
to
<ul>
<li>Semantic Cell 1</li><li>Semantic Cell 2</li><li>Semantic Cell 3</li><li>Pretty Cell 4</li><li>Pretty Cell 5</li><li>Pretty Cell 6</li>
</ul>
OR:
Pure css solution:
ul{font-size:0;}
li{font-size:1rem;}