CSS transform-box Property - Playground Example

<!DOCTYPE html><html><head><style type="text/css">/* Layout */
body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  margin: 0;
  background: #f6f8fa;
}

.wrapper {
  display: flex;
  gap: 24px;
  padding: 24px;
}

.card {
  background: #fff;
  border-radius: 8px;
  padding: 16px;
  box-shadow: 0 6px 18px rgba(20, 30, 40, 0.08);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.label {
  font-size: 13px;
  color: #333;
}

/* SVG styling */
.svg {
  width: 220px;
  height: 220px;
  overflow: visible;
  background: linear-gradient(180deg, rgba(0,0,0,0.02), transparent);
  border-radius: 6px;
  padding: 8px;
}

.reference line {
  stroke: #e6e9ee;
  stroke-width: 1;
}

.reference circle {
  fill: #666;
  opacity: 0.6;
}

.bg-rect {
  fill: none;
  stroke: #e0e6ef;
  stroke-width: 1.5;
}

.shape {
  fill: #ffcc33;
  stroke: #333;
  stroke-width: 1.5;
  /* center-based transform origin; transform-box decides which box "center" refers to */
  transform-origin: center;
  transition: transform 300ms ease;
}

/* Demonstrate difference between transform-box values */
.shape.view {
  transform-box: view-box; /* transforms use the SVG viewport (viewBox) as reference */
  transform: rotate(25deg);
}

.shape.fill {
  transform-box: fill-box; /* transforms use the element's own bounding box as reference */
  transform: rotate(25deg);
}

/* hover to emphasize the pivot difference */
.card:hover .shape {
  transform: rotate(45deg);
}
</style></head><body><div class="wrapper">
  <div class="card">
    <div class="label">transform-box: view-box</div>
    <svg viewBox="0 0 100 100" class="svg">
      <!-- reference: SVG viewport center -->
      <g class="reference">
        <line x1="0" y1="50" x2="100" y2="50" />
        <line x1="50" y1="0" x2="50" y2="100" />
        <circle cx="50" cy="50" r="2" />
      </g>

      <!-- the yellow rectangle will be rotated around the SVG viewBox center -->
      <rect x="10" y="30" width="30" height="40" class="shape view" />

      <!-- a second rectangle to show different bounding boxes in the same SVG -->
      <rect x="60" y="20" width="30" height="60" class="bg-rect" />
    </svg>
  </div>

  <div class="card">
    <div class="label">transform-box: fill-box</div>
    <svg viewBox="0 0 100 100" class="svg">
      <g class="reference">
        <line x1="0" y1="50" x2="100" y2="50" />
        <line x1="50" y1="0" x2="50" y2="100" />
        <circle cx="50" cy="50" r="2" />
      </g>

      <!-- the yellow rectangle will be rotated around its own bounding box center -->
      <rect x="10" y="30" width="30" height="40" class="shape fill" />

      <rect x="60" y="20" width="30" height="60" class="bg-rect" />
    </svg>
  </div>
</div></body></html>