Help needed - Browser mod css

I have a popup page for which I would like to tweak the layout. An more particularly I would like to add space between the edges (right, left and bottom) of the host card and the other cards. Can someone help me?
Here is the code snippet I have and the result:

action: fire-dom-event
browser_mod:
  service: browser_mod.popup
  data:
    title: System monitoring

    content:
      type: vertical-stack
      cards:
        - type: horizontal-stack
          cards:
            - type: tile
              entity: sensor.ipv4_address_eth0
            - type: tile
              entity: sensor.ipv6_address_eth0
        - type: horizontal-stack
          cards:
            - type: tile
              entity: sensor.processor_temperature
            - type: tile
              entity: sensor.processor_use
        - type: horizontal-stack
          cards:
            - type: tile
              entity: sensor.disk_use_percent_config
            - type: tile
              entity: sensor.disk_use
            - type: tile
              entity: sensor.disk_free

And by the way, is there also a way to center the ‘x’ in the upper left corner?

Many thanks