piskel/src/css/toolbox.css

.toolbox-container {
  border: 2px solid #888;
  font-size: medium;
  color: white;
  text-align: left;
  border-radius: 2px;
  margin-top: 5px;
  overflow: hidden;
}

.toolbox-title {
  padding: 8px;
  margin: 0;
  font-size: 15px;
  /* reset for firefox */
  height: 16px;
  background: #222;
}

.toolbox-buttons {
  flex-shrink: 0;
  overflow: hidden;
  border-top: 1px solid #666;
  border-bottom: 1px solid #222;
}

.toolbox-buttons .button {
  /* Override border propery on .button elements from form.css */
  border-width: 0 1px 0 0;
}

.toolbox-buttons button:last-child {
  border-right-width: 0;
}