line {
stroke-linecap: round;
}
.stroked {
stroke: magenta;
stroke-width: 1;
}
:not(.stroked) {
stroke: teal;
stroke-width: 0.25;
}
<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
<line x1="20" y1="50" x2="50" y2="10"></line>
<line x1="50" y1="10" x2="80" y2="50"></line>
<line class="stroked" x1="80" y1="50" x2="20" y2="50"></line>
</svg>