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Themes#

lantern uses the Base16 theming system for customizing the appearance of your presentations. Base16 provides a standardized way to define color schemes that work consistently across dark and light backgrounds.

Base16 Color System#

Base16 defines 16 semantic colors (base00 through base0F) that serve specific purposes:

Background Shades#

  • base00-03: Background colors from darkest to lighter (or lightest to darker in light themes)

Foreground Shades#

  • base04-07: Foreground colors from darker to lightest (or lightest to darker in light themes)

Accent Colors#

  • base08: Red (variables, deletion)
  • base09: Orange (integers, constants, emphasis)
  • base0A: Yellow (classes, list markers)
  • base0B: Green (strings, code blocks)
  • base0C: Cyan (links, support functions)
  • base0D: Blue (functions, headings)
  • base0E: Magenta (keywords, strong emphasis)
  • base0F: Brown (deprecated, special)

Color Mapping#

lantern maps base16 colors to semantic roles:

Content Colors#

  • Headings (base0D): Blue accent for slide titles
  • Body text (base05): Main foreground color
  • Strong/Bold (base0E): Magenta for emphasis
  • Emphasis/Italic (base09): Orange for subtle emphasis
  • Code blocks (base0B): Green for fenced code
  • Inline code background (base02): Selection background
  • Links (base0C): Cyan for hyperlinks
  • Accents (base08): Red for highlights
  • List markers (base0A): Yellow for bullets/numbers
  • Dimmed elements (base03): Comments, borders, rules

UI Chrome Colors#

  • UI background (base00): Status bar and UI backgrounds
  • UI borders (base04): Window and panel borders
  • UI titles (base06): Bright text for UI elements
  • UI text (base07): Brightest text for status bars

Available Themes#

lantern includes 10 prebuilt base16 themes, embedded at compile time:

Catppuccin#

  • catppuccin-mocha - Dark theme with pastel colors
  • catppuccin-latte - Light theme with warm tones

Gruvbox Material#

  • gruvbox-material-dark - Retro dark theme with warm colors
  • gruvbox-material-light - Retro light theme

Nord#

  • nord - Arctic-inspired dark theme with cool blues
  • nord-light - Nord palette adapted for light backgrounds

Oxocarbon#

  • oxocarbon-dark - IBM's modern dark theme (default)
  • oxocarbon-light - IBM's modern light theme

Solarized#

  • solarized-dark - Ethan Schoonover's precision dark palette
  • solarized-light - Solarized adapted for light backgrounds

Using Themes#

Via Frontmatter#

Specify a theme in your slide deck's YAML frontmatter:

---
theme: catppuccin-mocha
---

# Your First Slide

Content here

Or with TOML frontmatter:

+++
theme = "nord"
+++

# Your First Slide

Via Command Line#

Override the theme with the --theme flag:

lantern present presentation.md --theme nord
lantern print presentation.md --theme catppuccin-latte

Via Environment Variable#

Set a default theme using the LANTERN_THEME environment variable:

export LANTERN_THEME=gruvbox-material-dark
lantern present presentation.md

Theme Priority#

When multiple theme sources are specified, the priority order is:

  1. Command line flag (--theme)
  2. Frontmatter metadata (theme: field)
  3. Environment variable (LANTERN_THEME)
  4. Default theme (nord for dark terminals, nord-light for light terminals)

Custom Themes (Coming Soon)#

Future versions will support loading custom base16 YAML themes from:

  • ~/.config/slides/themes/ directory
  • --theme-file command line flag

Base16 YAML format:

system: "base16"
name: "My Custom Theme"
author: "Your Name"
variant: "dark"  # or "light"
palette:
  base00: "#1a1b26"
  base01: "#16161e"
  base02: "#2f3549"
  base03: "#444b6a"
  base04: "#787c99"
  base05: "#a9b1d6"
  base06: "#cbccd1"
  base07: "#d5d6db"
  base08: "#c0caf5"
  base09: "#a9b1d6"
  base0A: "#0db9d7"
  base0B: "#9ece6a"
  base0C: "#b4f9f8"
  base0D: "#2ac3de"
  base0E: "#bb9af7"
  base0F: "#f7768e"

You can find thousands of base16 themes at the Base16 Gallery.

Rendering Features#

The printer uses Unicode box-drawing characters for clean visual output:

  • ▉ ▓ ▒ ░ ▌ for heading levels (h1-h6)
  • ─ and ═ for horizontal rules
  • │ for blockquote borders and table dividers
  • • for unordered list markers

Tables automatically calculate column widths based on content and available terminal width.

Code blocks support syntax highlighting through Syntect, which automatically adapts to your selected theme's light/dark variant.