Center input_number input box

I’m trying to center the input box for an input_number.

type: custom:layout-card
layout_type: custom:vertical-layout
layout: {}
  - type: entities
      - entity: input_number.convert_from
        name: ' '
        icon: none
  - type: markdown
    content: >
      <some content>


I’ve tried a few things with card_mod. For example:

        style: |
          ha-textfield {
            text-align: center;

but nothing seems to move the needle.

Am I missing something simple? Are there any other cards that will render a input_number as a box? Every card I’ve tried besides entities renders it as a value that pulls up a properties box to modify it.