Create visual borders between elements on the same line - html

Question

I'd like the have a visual border, pipe or some other separator between the <span> elements in the following snippet. The trouble is that when they flow into a new line I end up with a border at the beginning of the line. How can i apply some kind of border between elements only when they are on the same line? I am completely open to changing the markup or taking another approach, however I've tried a number of things from flexbox to floats so far without success.
Stipulations:
I do not want to use javascript for this.
span content is dynamic so media queries won't work since I can't know the width of the elements or where they might break.
Is this even possible? I've already looked at this similar question but the answers there either use js or media queries.
The snippet below is a basic example and I've put the spans in a resizeable div only to demonstrate the flow problem at smaller widths.
.resizable {
resize: horizontal;
overflow: scroll;
border: 1px solid black;
height: 95vh;
box-sizing: border-box;
min-width: 120px;
max-width: 100%;
padding: 10px;
}
span {
font-size: 18px;
font-family: sans-serif;
}
span+span {
margin-left: 10px;
border-left: 2px solid #aaa;
padding-left: 10px;
display: inline-block;
}
<div class="resizable">
<span>dog</span><span>cat</span><span>elephant</span><span>potato</span><span>boston clam chowder</span>
</div>

Answer 1

You can fix this by using a container with the overflow hidden, and a negative margin to “drag” the elements at the beginning of the line outside of that overflow area.
(In this particular example the overflow:hidden is not really necessary, the outer scrolling element already takes care of that, but in different scenarios it might be needed.)
The 1.5em value used here is a bit of a magic number; you might want to replace it with a pixel value, since you’re using pixels for the border and its spacing from the text already - but in general, you should be able to find “working” values with a little bit of experimentation.
.resizable {
resize: horizontal;
overflow: scroll;
border: 1px solid black;
height: 95vh;
box-sizing: border-box;
min-width: 120px;
max-width: 100%;
padding: 10px;
}
.container {
margin-left: -1.5em;
width: calc(100% + 1.5em);
}
span {
font-size: 18px;
font-family: sans-serif;
margin-left: 10px;
border-left: 2px solid #aaa;
padding-left: 10px;
display: inline-block;
}
<div class="resizable">
<div class="container">
<span>dog</span><span>cat</span><span>elephant</span><span>potato</span><span>boston clam chowder</span><span>dog</span><span>cat</span><span>elephant</span><span>potato</span><span>boston clam chowder</span><span>dog</span><span>cat</span><span>elephant</span><span>potato</span><span>boston clam chowder</span>
</div>
</div>

Answer 2

Here's a pure CSS method that also works for elements that are centered.
The ::before and ::after of adjacent tiles are used to create a dark strip between the elements, then, the ::before of the container clips the lighter stuff out of existence.
Downsides - Getting the perfect color can be tricky as there's lots of maths involved.
section {
text-align: center;
position: relative;
}
section::before {
/* Clip light areas to pure white, leaving only boarders*/
mix-blend-mode: color-dodge;
background: #bbb;
z-index: -1000;
/* Fill Parent */
display: block;
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
content: "";
}
span {
position: relative;
display: inline-block;
box-sizing: border-box;
padding: 10px;
}
/* Spans slightly overlap creating darker lines between elements*/
span::before {
left: -1px;
}
span::after {
right: -1px;
}
span::before, span::after {
position: absolute;
content: "";
display: block;
width: 10px;
height: 100%;
background: #555;
top: 0;
z-index: -1001;
mix-blend-mode: multiply;
}
<section>
<span>Hello</span><span>Cats</span><span>Fish</span><span>Dogs</span><span>Hello</span><span>Cats</span><span>Fish</span><span>Dogs</span><span>Hello</span><span>Cats</span><span>Fish</span><span>Dogs</span>
</section>
For some reason, this code does not work in Stackoverflow's JSFiddle. Here's a link to JSFiddle where it does work:
https://jsfiddle.net/mdsimmo/vwu7xbjp/2/