Card volume dot.

        - type: custom:button-card # Soggiorno
          icon: mdi:circle-slice-8
          entity: media_player.soggiorno
          aspect_ratio: 3/1
          name: Vol. Soggiorno
          styles:
            card:
              - background: none
            grid:
              - position: relative
            custom_fields:
              notification:
                - background-color: >
                    [[[
                      if (states['sensor.volume_alexa_soggiorno'].state == 0)
                        return "green";
                      return "red";
                    ]]]
                - border-radius: 50%
                - position: absolute
                - left: 60%
                - top: 10%
                - height: 20px
                - width: 20px
                - font-size: 15px
                - line-height: 20px
          custom_fields:
            notification: >
              [[[ return Math.floor(states['sensor.volume_alexa_soggiorno'].state ) ]]]