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HTML

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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div class="panel" id="panel">
  <div class="frame rim"></div>
  <div class="frame accent"></div>
  <div class="frame accent glow"></div>
  <div class="circle icon">🌭</div>
  <div class="content">
    Lorem ipsum dolor sit, amet consectetur adipisicing elit. Magni harum vitae, ex ad aut corrupti corporis molestias velit exercitationem numquam cupiditate fuga, esse maxime officiis beatae molestiae odio in dolore!
  </div>
</div>
!

CSS 

              
                .panel {
  position: relative;
  padding: 1em;
  box-sizing: border-box;
  width: fit-content;
}

.panel .frame,
.panel .frame::before {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  box-sizing: border-box;
}

.panel .icon {
  position: absolute;
  top: 100%;
  left: 50%;
  width: 45px;
  height: 45px;
  background-color: #111216;
  box-shadow: inset 0 0 0 1px #8bc34a;
  border-radius: 50%;
  transform: translateX(-50%) translateY(-50%);
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Gray border */
.frame.rim {
  border: 1px solid #303030;
  box-shadow:
    inset 0 0 0 1px #0a0a0a,
    0 0 0 1px #0a0a0a;
  background-color: #111216;

  clip-path: var(--fill-path);
}

/* Green accent edges */
.frame.accent::before {
  content: '';
  background-image: linear-gradient(
    to top,
    #8bc34a,
    #558b2f99 25%,
    transparent 70%
  );
  clip-path: var(--outline-path);
}

/* Glow is just a copy of the accent frame with a blur filter */
.frame.accent.glow {
  filter: blur(4px);
}

.panel .content {
  min-width: 100px;
  min-height: 100px;
  width: 280px;
  height: 120px;
  position: relative;
  z-index: 1;
  font-size: smaller;
  resize: both;
  overflow: auto;
  /* Add some cushion at the bottom to avoid spilling over the icon */
  margin-bottom: 1.5em;
}

body {
  background-color: #0b0c0d;
  color: silver;
  font-family: Segoe UI,Helvetica Neue,Tahoma,Geneva,Verdana,sans-serif;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  margin: 0;
}
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JS 

              
                // Gap between the icon and panel's borders
const gutter = 4

/**
 * Recomputes the clip paths for the panel: a "fill path" for the background
 * and an "outline" path for the border. Punches a hole on the bottom edge
 * to make space for the icon. This expects the given panel to have a child
 * node with the "icon" class.
 * @param {HTMLElement} $el
 */
const updateClipPath = ($el) => {
  const $icon = $el.querySelector('.icon')
  const iconBox = $icon.getBoundingClientRect()
  const panelBox = $el.getBoundingClientRect()

  const iconWidth = iconBox.width
  const iconHeight = iconBox.height

  // Sort out where we need to go: the top, left, and right sides of the
  // panel are simple straight lines, but we need to stop at the sides of
  // the icon to create an arc around it.
  const w = panelBox.width
  const h = panelBox.height
  const rx = iconWidth / 2 + (gutter / 2)
  const ry = iconHeight / 2 + (gutter / 2)
  const ix1 = iconBox.x - panelBox.x - gutter
  const ix2 = ix1 + iconWidth + gutter * 2

  // Start with the fill path: trace around the edges of the panel clockwise
  // until we meet back at the top left corner
  const fillPath = [
    'M0,0',
    `L${w},0`,
    `L${w},${h}`,
    `L${ix2},${h}`,
    `A ${rx} ${ry} 0 0 0 ${ix1},${h}`,
    `L0,${h}`,
    'L0,0',
  ]

  // The outline path is an extension of the fill path: move 1px inward, then
  // move back around counter-clockwise until we come back to 1,1
  const outlinePath = fillPath.concat(
    'L1,1',
    `L1,${h - 1}`,
    `L${ix1 - 1},${h - 1}`,
    `A ${rx + 1} ${ry + 1} 0 0 1 ${ix2 + 1},${h - 1}`,
    `L${w - 1},${h - 1}`,
    `L${w - 1},1`,
    'L1,1',
  )

  // Set the fill and outline paths as CSS variables on the panel element
  $el.style.setProperty('--fill-path', `path('${fillPath.join(' ')}')`)
  $el.style.setProperty('--outline-path', `path('${outlinePath.join(' ')}')`)
}

document.addEventListener('DOMContentLoaded', () => {
  // Set up a ResizeObserver and attach it to the panel: any time the panel's
  // dimensions change, we'll recompute the path
  const $panel = document.getElementById('panel')
  const observer = new ResizeObserver(() => updateClipPath($panel))
  observer.observe($panel)

  updateClipPath($panel)
})
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999px

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