Confused about how to apply styles to the buttons

[siegeld]

I have the following lovelace code. The goal is for the buttons to be set to be a fixed width with padding and margins applied. Unfortunately, the style does not get applied to the buttons, as I can see from DOM inspection. Not sure what I am doing wrong. Any help would be appreciated.

- type: vertical-stack
  title: Test
  cards:
    - type: custom:mod-card
      style: |
            paper-buttons-row {
              display: flex;
              justify-content: space-between;
            }
            paper-buttons-row paper-button {
              width: calc(100% / 3 - 20px) !important; /* Adjust width to account for padding and margin */
              padding: 50px !important; /* Add padding for space within the button */
              margin: 50px !important; /* Add margin for space around the button */
            }
      card:
        type: custom:paper-buttons-row
        preset: mushroom
        base_config:
          layout: icon|name
          icon: "mdi:speaker"
        buttons:
            - type: button
              name: "Testing One Two"
            - type: button
              name: "Off"
            - type: button
              name: "On"