How to create a down arrow using CSS?

Question

I try to do an arrow with transparent color inside and coloured border but I'm new in this world . Someone can help me to do something like this: arrow down with text inside

My code:

.pentagon {
    position: relative;
    width: 350px;
    top:20rem;
    left: 20rem;
    border-width: 80px 0 100px 0;
    border-style: solid;
    border-color: #01ff70 transparent;
}
.pentagon:before {
    content: "";
    position: absolute;
    height: 0;
    width: 0;
    left: -7.5rem;
    border-width: 100px 300px 300px;
    border-style: solid;
    border-color: transparent transparent #01ff70;
    transform: rotate(180deg);
}

Answer 1

I would build this with multiple gradient to create each line:

.arrow {
  width:200px;
  height:200px;
  background:

    linear-gradient(blue,blue)  top center/ 100px 3px,
    
    linear-gradient(blue,blue)  calc(50% - 50px) 0/3px 50%,
    linear-gradient(blue,blue)  calc(50% + 50px) 0/3px 50%,
    
    linear-gradient(blue,blue)  0 50%/51px 3px,
    linear-gradient(blue,blue)  100% 50%/51px 3px,
    
    linear-gradient(to bottom right,
      transparent calc(50% - 2px),blue calc(50% - 2px),
      calc(50% + 2px),transparent calc(50% + 2px)) 100% 100%/50% 50%,
    linear-gradient(to bottom left,
      transparent calc(50% - 2px),blue calc(50% - 2px),
      calc(50% + 2px),transparent calc(50% + 2px)) 0 100%/50% 50%;
    
  background-repeat:no-repeat;
  text-align:center;
  line-height:220px;
}

<div class="arrow">
  text inside
</div>

And with some CSS variable to control the different values:

.arrow {
  --c:blue; /*main color*/
  --t:2px; /*thickness*/
  --d: 100px; /*top length*/
  --p:50%; /*percentage of top*/
  
  --g:linear-gradient(var(--c),var(--c));
  width:200px;
  height:200px;
  background:
    /*1*/
    var(--g) top center/ var(--d) var(--t),
    /*2*/
    var(--g)  calc(50% - var(--d)/2) 0/var(--t) calc(var(--p) + var(--t)/2),
    var(--g)  calc(50% + var(--d)/2) 0/var(--t) calc(var(--p) + var(--t)/2),
    /*3*/
    var(--g)  left  0 top var(--p)/calc(50% - var(--d)/2) var(--t),
    var(--g)  right 0 top var(--p)/calc(50% - var(--d)/2) var(--t),
    /*4*/
    linear-gradient(to bottom right,
      transparent calc(50% - var(--t)/2 - 1px),var(--c) calc(50% - var(--t)/2),
      calc(50% + var(--t)/2),transparent calc(50% + var(--t)/2 + 0.5px)) 100% 100%/50% calc(100% - var(--p)),
    linear-gradient(to bottom left,
      transparent calc(50% - var(--t)/2 - 1px),var(--c) calc(50% - var(--t)/2),
      calc(50% + var(--t)/2),transparent calc(50% + var(--t)/2 + 0.5px)) 0 100%/50% calc(100% - var(--p));
    
  background-repeat:no-repeat;
  display:inline-block;  
  text-align:center;
  line-height:220px;
}

<div class="arrow">
  text inside 
</div>
<div class="arrow" style="--c:red;--t:5px;--d:40px;--p:40%">
 text inside
</div>
<div class="arrow" style="--c:green;--t:3px;--d:70px;--p:60%">
 text inside
</div>

1. a line placed at the top center with a width equal to --d and a height equal to --t
2. The two vertical lines with a width equal to --t and a height equal --p + half the thickness to have them correctly linked with the bottom part. We place the first line at the top 0 and from the center we remove half --d so it start at the left of the top line. Same logic with the other line at the right.
3. The two horizontal lines with a width equal to half the width left by the top line (100% - var(--d))/2 and a height equal to --t. Their placement is easy to find. the left one at 0 from the left and --p from the top. Same logic for the right one.
4. The two diagonal lines are two gradient that will take half the width and 100% - var(--p). Here we play with the coloration to color only a diganonal part and we keep the remaining transparent.

---

If you want more, we can add a coloration inside the arrow:

.arrow {
  --c:blue; /*main color*/
  --b:red; /*background color*/
  --t:2px; /*thickness*/
  --d: 100px; /*top length*/
  --p:50%; /*percentage of top*/
  
  --g:linear-gradient(var(--c),var(--c));
  width:200px;
  height:200px;
  background:
    /*1*/
    var(--g) top center/ var(--d) var(--t),
    /*2*/
    var(--g)  calc(50% - var(--d)/2) 0/var(--t) calc(var(--p) + var(--t)/2),
    var(--g)  calc(50% + var(--d)/2) 0/var(--t) calc(var(--p) + var(--t)/2),
    /*3*/
    var(--g)  left  0 top var(--p)/calc(50% - var(--d)/2) var(--t),
    var(--g)  right 0 top var(--p)/calc(50% - var(--d)/2) var(--t),
    /*4*/
    linear-gradient(to bottom right,
      var(--b) calc(50% - var(--t)/2 - 1px),var(--c) calc(50% - var(--t)/2),
      calc(50% + var(--t)/2),transparent calc(50% + var(--t)/2 + 0.5px)) 100% 100%/50% calc(100% - var(--p)),
    linear-gradient(to bottom left,
      var(--b) calc(50% - var(--t)/2 - 1px),var(--c) calc(50% - var(--t)/2),
      calc(50% + var(--t)/2),transparent calc(50% + var(--t)/2 + 0.5px)) 0 100%/50% calc(100% - var(--p)),
     /*5*/
     linear-gradient(var(--b),var(--b)) center top/var(--d) var(--p);
  background-repeat:no-repeat;
  display:inline-block;  
  text-align:center;
  line-height:220px;
}

<div class="arrow">
  text inside
</div>
<div class="arrow" style="--c:red;--b:yellow;--t:5px;--d:40px;--p:40%">
  text inside
</div>
<div class="arrow" style="--c:green;--b:pink;--t:3px;--d:70px;--p:60%">
  text inside
</div>