{# Open Graph + Twitter Card — shared site image on every page #}
{% set og_image = get_url(path='og.jpg', trailing_slash=false) %}
<meta property="og:type" content="website" />
<meta property="og:site_name" content="{{ config.extra.site_title }}" />
<meta property="og:title" content="{% if page %}{{ page.title }}{% elif section %}{{ section.title }}{% else %}{{ config.title }}{% endif %}" />
<meta property="og:description" content="{% if page and page.description %}{{ page.description }}{% elif section and section.description %}{{ section.description }}{% else %}{{ config.description }}{% endif %}" />
<meta property="og:url" content="{% if page %}{{ page.permalink }}{% elif section %}{{ section.permalink }}{% else %}{{ config.base_url }}{% endif %}" />
<meta property="og:image" content="{{ og_image }}" />
<meta property="og:image:width" content="1200" />
<meta property="og:image:height" content="630" />
<meta property="og:image:alt" content="{{ config.extra.site_title }} — free, open textbooks for every learner" />
<meta name="twitter:card" content="summary_large_image" />
<meta name="twitter:title" content="{% if page %}{{ page.title }}{% elif section %}{{ section.title }}{% else %}{{ config.title }}{% endif %}" />
<meta name="twitter:description" content="{% if page and page.description %}{{ page.description }}{% elif section and section.description %}{{ section.description }}{% else %}{{ config.description }}{% endif %}" />
<meta name="twitter:image" content="{{ og_image }}" />
<meta name="twitter:image:alt" content="{{ config.extra.site_title }} — free, open textbooks for every learner" />