Option 2 (larger canvas — NOT applied here): the `size:` frontmatter only accepts sizes the active theme has declared via @size. The bundled `default`/`gaia` themes only declare 16:9 (1280x720) and 4:3 (960x720). To get a 1920x1080 canvas you must register a custom theme via marp.config.mjs / --theme that contains @size fhd 1920px 1080px; and then reference it as `size: fhd`. Inline <style> blocks cannot declare theme metadata, so a one-file demo of option 2 isn't possible without touching the build pipeline.