Может быть простой фон на контейнере:
background:linear-gradient(#084085,#084085) center/100% 5px no-repeat;
.default-step {
height: 100px;
max-width: 100px;
text-align: center;
border: 5px solid #3A83C5;
border-radius: 50%;
background: #FFF;
color: #084085;
line-height: 3em;
flex: 1 1 auto;
}
.steps {
display: flex;
justify-content: space-between;
/*Add this code*/
background:linear-gradient(#084085,#084085) center/100% 5px no-repeat;
}
<div class="steps">
<div id="circle-step-1" class="default-step">STEP 1</div>
<div id="circle-step-2" class="default-step">STEP2</div>
<div id="circle-step-3" class="default-step">STEP 3</div>
<div id="circle-step-4" class="default-step">STEP 4</div>
<div id="circle-step-5" class="default-step">STEP 5</div>
</div>
БОНУС
Если вы хотите иметь стрелки, вы можете попробовать это:
.default-step {
height: 100px;
max-width: 100px;
text-align: center;
border: 5px solid #3A83C5;
border-radius: 50%;
background: #FFF;
color: #084085;
line-height: 3em;
flex: 1 1 auto;
position:relative;
box-sizing:border-box;
}
.default-step:not(:first-child):before {
content:"";
position:absolute;
height:20px;
width:10px;
top:calc(50% - 10px);
left:-15px;
background-image:
linear-gradient(to bottom right,#084085 50%, white 0),
linear-gradient(to top right,#084085 50%, white 0);
background-position:bottom, top;
background-size:100% 50%;
background-repeat:no-repeat;
}
.steps {
display: flex;
justify-content: space-between;
/*Add this code*/
background:linear-gradient(#084085,#084085)0 50%/100% 5px no-repeat;
}
<div class="steps">
<div id="circle-step-1" class="default-step">STEP 1</div>
<div id="circle-step-2" class="default-step">STEP2</div>
<div id="circle-step-3" class="default-step">STEP 3</div>
<div id="circle-step-4" class="default-step">STEP 4</div>
<div id="circle-step-5" class="default-step">STEP 5</div>
</div>
А вот полный код с прозрачностью :
body {
background:linear-gradient(to right,pink,lightblue);
}
.default-step {
height: 100px;
max-width: 100px;
text-align: center;
border: 5px solid #3A83C5;
border-radius: 50%;
color: #084085;
line-height: 3em;
flex: 1 1 auto;
position:relative;
box-sizing:border-box;
}
.default-step:not(:first-child):before {
content:"";
position:absolute;
height:20px;
width:10px;
top:calc(50% - 10px);
left:-15px;
background-image:
linear-gradient(to bottom right,#084085 50%, transparent 50.5%),
linear-gradient(to top right,#084085 50%, transparent 50.5%);
background-position:bottom, top;
background-size:100% 50%;
background-repeat:no-repeat;
}
.steps {
display: flex;
justify-content: space-between;
/*Add this code*/
background:linear-gradient(to right, transparent 100px, #084085 100px, #084085 calc(100% - 5px),transparent 0) 0 50%/calc((100% - 100px)/4) 5px repeat-x;
}
<div class="steps">
<div id="circle-step-1" class="default-step">STEP 1</div>
<div id="circle-step-2" class="default-step">STEP2</div>
<div id="circle-step-3" class="default-step">STEP 3</div>
<div id="circle-step-4" class="default-step">STEP 4</div>
<div id="circle-step-5" class="default-step">STEP 5</div>
</div>