How to achieve curved top pointer

Question

Can anyone please help with this? How to achieve the attached button with CSS only(no image)?

This is my code so far:

.triangle-up {
  width: 0;
  height: 0;
  border-left: 25px solid transparent;
  border-right: 25px solid transparent;
  border-bottom: 50px solid #555;
}

<div class="triangle-up"></div>

Answer 1

One option is to create a normal rectangle and then position two circles over it, such that they create a curved point.

In the demo below, this rectangle is represented by the .point div, and the circles are represented by the pseudo-elements ::before and ::after.

.caption {
  position: relative;
  width: 350px;
 margin-top: 40px;
}

.caption>.content {
  width: 100%;
  height: 100%;
  padding: 10px;
  box-sizing: border-box;
  border-radius: 30px;
  background-color: green;
  color: white;
  text-align: center;
}

.caption>.point {
  position: absolute;
  left: 50%;
  top: -30px;
  width: 30%;
  height: 30px;
  transform: translateX(-50%) translateZ(1px);
  overflow: hidden;
  background-color: green;
}

.caption>.point::before,
.caption>.point::after {
  content: '';
  display: block;
  width: 100%;
  height: 200%;
  position: absolute;
  top: 0;
  left: 0;
  border-radius: 100%;
  background-color: white;
}

.caption>.point::before {
  transform: translateX(-49%) translateY(-50%);
}

.caption>.point::after {
  transform: translateX(49%) translateY(-50%);
}

<div class="caption">
  <div class="point"></div>
  <div class="content">This is some text!</div>
</div>

Here is a more visual demonstration of what the code is actually doing. The ::before and ::after elements are represented by the red circles. I've reduced the transparency of their fill to 50% so you can see which portion of the .point div they're cutting off.

.caption {
  position: relative;
  width: 350px;
 margin-top: 40px;
}

.caption>.content {
  width: 100%;
  height: 100%;
  padding: 10px;
  box-sizing: border-box;
  border-radius: 30px;
  background-color: green;
  color: white;
  text-align: center;
}

.caption>.point {
  position: absolute;
  left: 50%;
  top: -30px;
  width: 30%;
  height: 30px;
  transform: translateX(-50%) translateZ(1px);
  background-color: green;
}

.caption>.point::before,
.caption>.point::after {
  content: '';
  display: block;
  width: 100%;
  height: 200%;
  position: absolute;
  top: 0;
  left: 0;
  border-radius: 100%;
  background-color: rgba(255,255,255,0.5);
  border: 1px solid red;
}

.caption>.point::before {
  transform: translateX(-49%) translateY(-50%);
}

.caption>.point::after {
  transform: translateX(49%) translateY(-50%);
}

<div class="caption">
  <div class="point"></div>
  <div class="content">This is some text!</div>
</div>