diff --git a/LICENSE b/LICENSE
index d0c07f2..b240a91 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2023 Alex Kotov
+Copyright (c) 2023-2024 Alex Kotov
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/exe/repubmark b/exe/repubmark
new file mode 100755
index 0000000..fca1e0c
--- /dev/null
+++ b/exe/repubmark
@@ -0,0 +1,46 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+lib = File.expand_path('../lib', __dir__).freeze
+$LOAD_PATH.unshift lib unless $LOAD_PATH.include? lib
+
+require 'bundler/setup'
+
+require 'repubmark'
+
+FORMATS = %w[word_count html gemtext].freeze
+
+$format = String(ARGV[0]).freeze
+raise "Invalid format: #{$format.inspect}" unless FORMATS.include? $format
+
+$template = $stdin.read.freeze
+
+$config = Repubmark::Config.new(
+  base_url: 'https://causa-arcana.com',
+  css_class_annotation: 'nice-annotation',
+  css_class_blockquote_figure: 'nice-blockquote',
+  css_class_figure_self: 'nice-figure',
+  css_class_figure_wrap: 'd-flex justify-content-center',
+  css_class_figures_left: 'col-xl-6',
+  css_class_figures_right: 'col-xl-6',
+  css_class_figures_wrap: 'row',
+  css_class_iframe_wrap: 'ratio ratio-16x9',
+  current_path: '/xx/blog/xxxx/xx/xx/xxx.xxx',
+  relative_urls: false,
+)
+
+$article = Repubmark::Elems::Article.new $config
+$article.tap do |article| # rubocop:disable Lint/UnusedBlockArgument
+  eval $template # rubocop:disable Security/Eval
+end
+
+case $format
+when 'word_count'
+  puts $article.word_count
+when 'html'
+  puts $article.to_html.strip
+when 'gemtext'
+  puts $article.to_gemtext.strip
+else
+  raise 'Unknown blog format'
+end
diff --git a/lib/repubmark.rb b/lib/repubmark.rb
new file mode 100644
index 0000000..ea23389
--- /dev/null
+++ b/lib/repubmark.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require 'cgi'
+require 'forwardable'
+require 'open3'
+require 'pathname'
+require 'uri'
+
+require_relative 'repubmark/config'
+require_relative 'repubmark/highlight'
+require_relative 'repubmark/setup'
+require_relative 'repubmark/titled_ref'
+
+require_relative 'repubmark/elems/base'
+
+# Top-level element
+require_relative 'repubmark/elems/article'
+
+# Always inside Article
+require_relative 'repubmark/elems/annotation'
+# Always inside Article, Chapter
+require_relative 'repubmark/elems/chapter'
+# Always inside Annotation, Blockquote, Chapter
+require_relative 'repubmark/elems/canvas'
+
+# Always inside Canvas
+require_relative 'repubmark/elems/blockquote'
+require_relative 'repubmark/elems/code_block'
+require_relative 'repubmark/elems/figures'
+require_relative 'repubmark/elems/iframe'
+require_relative 'repubmark/elems/paragraph'
+require_relative 'repubmark/elems/separator'
+
+# Always inside Canvas, Figures
+require_relative 'repubmark/elems/figure'
+# Always inside Canvas, ListItem
+require_relative 'repubmark/elems/list'
+# Always inside List
+require_relative 'repubmark/elems/list_item'
+
+# Always inside Caption, Quote
+require_relative 'repubmark/elems/joint'
+# Always inside Blockquote, Figure, ListItem, Paragraph
+require_relative 'repubmark/elems/caption'
+# Always inside Caption, Joint, Quote
+require_relative 'repubmark/elems/quote'
+
+# Always inside Joint
+require_relative 'repubmark/elems/abbrev'
+require_relative 'repubmark/elems/code_inline'
+require_relative 'repubmark/elems/fraction'
+require_relative 'repubmark/elems/note'
+require_relative 'repubmark/elems/section'
+require_relative 'repubmark/elems/special'
+require_relative 'repubmark/elems/text'
+require_relative 'repubmark/elems/link'
diff --git a/lib/repubmark/config.rb b/lib/repubmark/config.rb
new file mode 100644
index 0000000..b9d14de
--- /dev/null
+++ b/lib/repubmark/config.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module Repubmark
+  class Config
+    OPTIONAL_KEYS = %i[
+      base_url
+      css_class_annotation
+      css_class_blockquote_figure
+      css_class_blockquote_blockquote
+      css_class_blockquote_figcaption
+      css_class_figure_self
+      css_class_figure_wrap
+      css_class_figures_left
+      css_class_figures_right
+      css_class_figures_wrap
+      css_class_iframe_wrap
+      current_path
+      relative_urls
+    ].freeze
+
+    def initialize(**kwargs)
+      raise unless (kwargs.keys.sort - OPTIONAL_KEYS).empty?
+
+      @kwargs = kwargs.freeze
+    end
+
+    def [](key)
+      OPTIONAL_KEYS.include?(key) ? @kwargs[key] : @kwargs.fetch(key)
+    end
+  end
+end
diff --git a/lib/repubmark/elems/abbrev.rb b/lib/repubmark/elems/abbrev.rb
new file mode 100644
index 0000000..b329b34
--- /dev/null
+++ b/lib/repubmark/elems/abbrev.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Abbrev < Base
+      parents :Joint
+
+      attr_reader :abbrev, :transcript
+
+      def initialize(parent, abbrev, transcript)
+        super parent
+
+        self.abbrev = abbrev
+        self.transcript = transcript
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = 1
+
+      def to_html
+        %(<abbr title="#{escape_transcript}">#{escape_abbrev}</abbr>).freeze
+      end
+
+      def to_gemtext = abbrev
+
+    private
+
+      def abbrev=(abbrev)
+        @abbrev =
+          String(abbrev).split.join(' ').freeze.tap do |new_abbrev|
+            raise 'Empty string' if new_abbrev.empty?
+          end
+      end
+
+      def transcript=(transcript)
+        @transcript =
+          String(transcript).split.join(' ').freeze.tap do |new_transcript|
+            raise 'Empty string' if new_transcript.empty?
+          end
+      end
+
+      def escape_abbrev = CGI.escape_html(abbrev).freeze
+
+      def escape_transcript = CGI.escape_html(transcript).freeze
+    end
+  end
+end
diff --git a/lib/repubmark/elems/annotation.rb b/lib/repubmark/elems/annotation.rb
new file mode 100644
index 0000000..46b6db3
--- /dev/null
+++ b/lib/repubmark/elems/annotation.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Annotation < Base
+      parents :Article
+
+      def initialize(parent)
+        super parent
+        @canvas = Canvas.new self
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @canvas.word_count
+
+      def to_html
+        [
+          %(<div#{html_class(:annotation)}>\n),
+          @canvas.to_html,
+          "</div>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext = @canvas.to_gemtext
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def respond_to_missing?(method_name, _include_private)
+        @canvas.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @canvas.respond_to? method_name
+          @canvas.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/article.rb b/lib/repubmark/elems/article.rb
new file mode 100644
index 0000000..8c7561e
--- /dev/null
+++ b/lib/repubmark/elems/article.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Article < Base
+      attr_reader :config
+
+      def initialize(config) # rubocop:disable Lint/MissingSuper
+        @parent = nil
+        self.config = config
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count
+        (@annotation&.word_count || 0) +
+          (@chapter&.word_count || 0)
+      end
+
+      def to_html
+        [
+          setup.prologue,
+          @annotation&.to_html,
+          @chapter&.to_html,
+          setup.epilogue,
+        ].compact.join.freeze
+      end
+
+      def to_gemtext
+        [
+          setup.prologue,
+          @annotation&.to_gemtext,
+          @chapter&.to_gemtext,
+          setup.epilogue,
+        ].compact.join("\n\n\n").freeze
+      end
+
+      #################
+      # Setup methods #
+      #################
+
+      def setup(&)
+        @setup ||= Setup.new(&)
+      end
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def annotation
+        raise 'Annotation already exists' if @annotation
+        raise 'Annotation after chapter'  if @chapter
+
+        @annotation = Annotation.new self
+        yield @annotation
+        nil
+      end
+
+      def respond_to_missing?(method_name, _include_private)
+        chapter = @chapter || Chapter.new(self)
+        chapter.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        chapter = @chapter || Chapter.new(self)
+        if chapter.respond_to? method_name
+          @chapter = chapter
+          @chapter.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+
+    private
+
+      def config=(config)
+        unless config.instance_of? Config
+          raise TypeError, "Expected #{Config}, got #{config.class}"
+        end
+
+        @config = config
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/base.rb b/lib/repubmark/elems/base.rb
new file mode 100644
index 0000000..6feb062
--- /dev/null
+++ b/lib/repubmark/elems/base.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Base
+      attr_reader :parent
+
+      def initialize(parent)
+        self.parent = parent
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = 0
+
+      def to_html
+        raise NotImplementedError, "#{self.class}#to_html"
+      end
+
+      def to_gemtext
+        raise NotImplementedError, "#{self.class}#to_gemtext"
+      end
+
+      ##################
+      # Helper methods #
+      ##################
+
+      def config = parent.config
+
+      def setup = parent.setup
+
+      class << self
+        def parents(*args)
+          if @parents
+            raise ArgumentError, 'Invalid args' unless args.empty?
+
+            return @parents
+          end
+
+          @parents = args.map { |arg| "#{Elems}::#{arg}".freeze }.to_a.freeze
+          nil
+        end
+
+        def parent?(klass)
+          unless klass.instance_of? Class
+            raise TypeError, "Expected #{Class}, got #{klass.class}"
+          end
+
+          parents.include? klass.name
+        end
+      end
+
+    private
+
+      def parent=(parent)
+        unless parent.is_a? Base
+          raise TypeError, "Expected #{Base}, got #{parent.class}"
+        end
+
+        unless self.class.parent? parent.class
+          raise TypeError,
+                "Expected #{self.class.parents.join(', ')}, got #{parent.class}"
+        end
+
+        @parent = parent
+      end
+
+      def own_url(path)
+        config[:relative_urls] ? relative_url(path) : absolute_url(path)
+      end
+
+      def absolute_url(path)
+        base_url = String(config[:base_url]).strip.freeze
+        raise 'Invalid base URL' if base_url.empty?
+
+        path = "/#{path}" unless path.start_with? '/'
+        "#{base_url}#{path}"
+      end
+
+      def relative_url(path)
+        current_path = String(config[:current_path]).strip.freeze
+        raise 'Invalid current path URL' if current_path.empty?
+
+        Pathname
+          .new(path)
+          .relative_path_from("/#{current_path}/..")
+          .to_s
+          .freeze
+      end
+
+      def html_class(key)
+        if (value = config[:"css_class_#{key}"])
+          %( class="#{value}").freeze
+        else
+          ''
+        end
+      end
+
+      def count_words(str) = str.split.count
+    end
+  end
+end
diff --git a/lib/repubmark/elems/blockquote.rb b/lib/repubmark/elems/blockquote.rb
new file mode 100644
index 0000000..c019e50
--- /dev/null
+++ b/lib/repubmark/elems/blockquote.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Blockquote < Base
+      parents :Canvas
+
+      def initialize(parent)
+        super parent
+
+        @canvas = Canvas.new self
+        @caption = nil
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @canvas.word_count + (@caption&.word_count || 0)
+
+      def to_html
+        [
+          "<figure#{html_class(:blockquote_figure)}>\n",
+          "<blockquote#{html_class(:blockquote_blockquote)}>\n",
+          @canvas.to_html,
+          "</blockquote>\n",
+          caption_html,
+          "</figure>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext
+        [
+          @canvas.to_gemtext.split("\n").map { |s| "> #{s}\n" }.join,
+          caption_gemtext,
+        ].join.freeze
+      end
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def caption
+        @caption = Caption.new self
+        yield @caption
+        nil
+      end
+
+      def respond_to_missing?(method_name, _include_private)
+        @canvas.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @canvas.respond_to? method_name
+          raise 'Paragraph after caption' unless @caption.nil?
+
+          @canvas.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+
+    private
+
+      def caption_html
+        return if @caption.nil?
+
+        [
+          "<figcaption#{html_class(:blockquote_figcaption)}>\n",
+          @caption.to_html,
+          "</figcaption>\n",
+        ].join.freeze
+      end
+
+      def caption_gemtext
+        "#{@caption.to_gemtext}\n".freeze unless @caption.nil?
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/canvas.rb b/lib/repubmark/elems/canvas.rb
new file mode 100644
index 0000000..41e463a
--- /dev/null
+++ b/lib/repubmark/elems/canvas.rb
@@ -0,0 +1,94 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Canvas < Base
+      parents :Annotation, :Blockquote, :Chapter
+
+      def initialize(parent)
+        super parent
+        @items = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @items.sum(&:word_count)
+
+      def to_html = @items.map(&:to_html).join.freeze
+
+      def to_gemtext = @items.map(&:to_gemtext).join("\n").freeze
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def blockquote
+        blockquote = Blockquote.new self
+        @items << blockquote
+        yield blockquote
+        nil
+      end
+
+      def code_block(*args, **kwargs)
+        code_block = CodeBlock.new self, *args, **kwargs
+        @items << code_block
+        nil
+      end
+
+      def iframe(*args, **kwargs)
+        iframe = Iframe.new self, *args, **kwargs
+        @items << iframe
+        nil
+      end
+
+      def links_list
+        list = List.new self, links: true, ordered: false
+        @items << list
+        yield list
+        nil
+      end
+
+      def nice_figure(name, alt)
+        figure = Figure.new self, name, alt
+        @items << figure
+        yield figure if block_given?
+        nil
+      end
+
+      def nice_figures
+        figures = Figures.new self
+        @items << figures
+        yield figures
+        nil
+      end
+
+      def olist
+        list = List.new self, links: false, ordered: true
+        @items << list
+        yield list
+        nil
+      end
+
+      def paragraph
+        paragraph = Paragraph.new self
+        @items << paragraph
+        yield paragraph
+        nil
+      end
+
+      def separator
+        @items << Separator.new(self)
+        nil
+      end
+
+      def ulist
+        list = List.new self, links: false, ordered: false
+        @items << list
+        yield list
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/caption.rb b/lib/repubmark/elems/caption.rb
new file mode 100644
index 0000000..cf724b4
--- /dev/null
+++ b/lib/repubmark/elems/caption.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Caption < Base
+      include Joint::ForwardingBuilders
+
+      parents :Blockquote, :Figure, :ListItem, :Paragraph
+
+      def initialize(parent)
+        super parent
+        @items = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @items.sum(&:word_count)
+
+      def to_html
+        [
+          '<span>',
+          *@items.map(&:to_html),
+          '</span>',
+        ].map { |s| "#{s}\n" }.join.freeze
+      end
+
+      def to_gemtext = @items.map(&:to_gemtext).join(' ').strip.freeze
+
+      ##################
+      # Helper methods #
+      ##################
+
+      def empty? = @items.empty?
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def joint
+        joint = Joint.new self
+        yield joint
+        @items << joint
+        nil
+      end
+
+      def quote(str = nil)
+        quote = Quote.new self
+        case [!!str, block_given?]
+        when [true, false] then quote.text str
+        when [false, true] then yield quote
+        else
+          raise 'Invalid args'
+        end
+        @items << quote
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/chapter.rb b/lib/repubmark/elems/chapter.rb
new file mode 100644
index 0000000..3d48161
--- /dev/null
+++ b/lib/repubmark/elems/chapter.rb
@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Chapter < Base
+      parents :Article, :Chapter
+
+      def initialize(parent, level = 1, title = nil)
+        super parent
+        self.level = level
+        self.title = title
+        verify!
+
+        @canvas = Canvas.new self
+        @chapters = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count
+        (@title ? count_words(@title) : 0) +
+          @canvas.word_count +
+          @chapters.sum(&:word_count)
+      end
+
+      def to_html
+        [
+          build_title_html,
+          @canvas.to_html,
+          *@chapters.map(&:to_html),
+        ].join.freeze
+      end
+
+      def to_gemtext
+        [
+          build_title_gemtext,
+          @canvas.to_gemtext,
+          *@chapters.map(&:to_gemtext),
+        ].join.freeze
+      end
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def chapter(title)
+        chapter = Chapter.new self, @level + 1, title
+        @chapters << chapter
+        yield chapter
+        nil
+      end
+
+      def respond_to_missing?(method_name, _include_private)
+        @canvas.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @canvas.respond_to? method_name
+          raise 'Intro after chapters' unless @chapters.empty?
+
+          @canvas.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+
+    private
+
+      def level=(level)
+        level = Integer level
+        raise unless level.positive?
+
+        @level = level
+      end
+
+      def title=(title)
+        return @title = nil if title.nil?
+
+        title = String(title).strip.freeze
+        raise 'Empty title' if title.empty?
+
+        @title = title
+      end
+
+      def verify!
+        raise 'Non-empty title for level 1' if @level == 1 && @title
+        raise 'Empty title for level >= 2'  if @level != 1 && @title.nil?
+      end
+
+      def build_title_html
+        "<h#@level>#@title</h#@level>\n" if @level != 1
+      end
+
+      def build_title_gemtext
+        "\n#{'#' * @level} #@title\n\n" if @level != 1
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/code_block.rb b/lib/repubmark/elems/code_block.rb
new file mode 100644
index 0000000..350e1ac
--- /dev/null
+++ b/lib/repubmark/elems/code_block.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class CodeBlock < Base
+      parents :Canvas
+
+      attr_reader :syntax, :str, :indent
+
+      def initialize(parent, syntax, str, indent: 0)
+        super parent
+
+        self.syntax = syntax
+        self.str = str
+        self.indent = indent
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html = highlighted_str
+
+      def to_gemtext
+        [
+          "```\n",
+          "#{str.strip}\n",
+          "```\n",
+        ].join.freeze
+      end
+
+    private
+
+      def syntax=(syntax)
+        return @syntax = nil if syntax.nil?
+
+        unless syntax.instance_of? Symbol
+          raise TypeError, "Expected #{Symbol}, got #{syntax.class}"
+        end
+
+        @syntax = syntax
+      end
+
+      def str=(str)
+        str = String(str).freeze
+        raise 'Expected non-blank string' if str.strip.empty?
+
+        @str = str
+      end
+
+      def indent=(indent)
+        @indent = Integer indent
+        raise 'Expected non-negative number' if @indent.negative?
+      end
+
+      def highlighted_str
+        @highlighted_str ||= Highlight.call syntax, transformed_str
+      end
+
+      def transformed_str
+        @transformed_str ||=
+          str.lines.map { |line| "#{indentation}#{line}" }.join.freeze
+      end
+
+      def indentation
+        @indentation ||= (' ' * indent).freeze
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/code_inline.rb b/lib/repubmark/elems/code_inline.rb
new file mode 100644
index 0000000..5d6ba15
--- /dev/null
+++ b/lib/repubmark/elems/code_inline.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class CodeInline < Base
+      parents :Joint
+
+      def initialize(parent, str)
+        super parent
+        self.str = str
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html = "<code>#{CGI.escape_html(@str)}</code>".freeze
+
+      def to_gemtext = "«#{@str}»".freeze
+
+    private
+
+      def str=(str)
+        str = String(str).freeze
+        if str.include?("\n") || str.include?('«') || str.include?('»')
+          raise 'Invalid str'
+        end
+
+        @str = str
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/figure.rb b/lib/repubmark/elems/figure.rb
new file mode 100644
index 0000000..0e8c2c2
--- /dev/null
+++ b/lib/repubmark/elems/figure.rb
@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Figure < Base
+      parents :Canvas, :Figures
+
+      def initialize(parent, name, alt)
+        super parent
+
+        alt = String(alt).strip.split.join(' ').freeze
+        raise 'Empty alt text' if alt.empty?
+
+        @name = String(name).strip.freeze
+        @alt = alt
+        @caption = Caption.new self
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html
+        [
+          "<div#{html_class(:figure_wrap)}>\n",
+          "<figure#{html_class(:figure_self)}>\n",
+          "<img src=\"#{src}\" alt=\"#{CGI.escape_html(@alt)}\"/>\n",
+          "<figcaption>\n",
+          caption_html,
+          "</figcaption>\n",
+          "</figure>\n",
+          "</div>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext
+        caption = @caption.to_gemtext
+        caption = @alt if caption.empty?
+        "=> #{src} #{caption}\n".freeze
+      end
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def respond_to_missing?(method_name, _include_private)
+        @caption.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @caption.respond_to? method_name
+          @caption.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+
+    private
+
+      def src
+        @src ||= own_url "/assets/images/blog/#@name"
+      end
+
+      def caption_html
+        if @caption.empty?
+          "#{CGI.escape_html(@alt)}\n"
+        else
+          @caption.to_html
+        end
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/figures.rb b/lib/repubmark/elems/figures.rb
new file mode 100644
index 0000000..b109e18
--- /dev/null
+++ b/lib/repubmark/elems/figures.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Figures < Base
+      parents :Canvas
+
+      def initialize(parent)
+        super parent
+        @figures = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html
+        raise 'Expected two figures' unless @figures.size == 2
+
+        [
+          "<div#{html_class(:figures_wrap)}>\n",
+          *@figures.flat_map do |figure|
+            [
+              "<div#{html_class(:figures_left)}>\n",
+              figure.to_html,
+              "</div>\n",
+            ]
+          end,
+          "</div>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext = @figures.map(&:to_gemtext).join.freeze
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def figure(name, alt)
+        figure = Figure.new self, name, alt
+        @figures << figure
+        yield figure if block_given?
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/fraction.rb b/lib/repubmark/elems/fraction.rb
new file mode 100644
index 0000000..6ab8fa9
--- /dev/null
+++ b/lib/repubmark/elems/fraction.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Fraction < Base
+      parents :Joint
+
+      def initialize(parent, top, bottom)
+        super parent
+
+        @top    = Integer top
+        @bottom = Integer bottom
+
+        raise 'Expected top to be non-negative' if @top.negative?
+        raise 'Expected bottom to be positive' unless @bottom.positive?
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = 1
+
+      def to_html
+        "<sup>#@top</sup>&frasl;<sub>#@bottom</sub>".freeze
+      end
+
+      def to_gemtext = "#@top/#@bottom"
+    end
+  end
+end
diff --git a/lib/repubmark/elems/iframe.rb b/lib/repubmark/elems/iframe.rb
new file mode 100644
index 0000000..94c6513
--- /dev/null
+++ b/lib/repubmark/elems/iframe.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Iframe < Base
+      parents :Canvas
+
+      attr_reader :title, :src, :url
+
+      def initialize(parent, title, src, url = nil)
+        super parent
+
+        self.title = title
+        self.src = src
+        self.url = url || src
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html
+        [
+          "<div#{html_class(:iframe_wrap)}>\n",
+          "<iframe\n",
+          %(title="#{title}"\n),
+          %(src="#{src}"\n),
+          %(allowfullscreen=""\n),
+          %(frameborder="0"\n),
+          %(sandbox="allow-same-origin allow-scripts allow-popups"\n),
+          "></iframe>\n",
+          "</div>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext = "=> #{url} #{title}\n"
+
+    private
+
+      def title=(title)
+        title = String(title).strip.freeze
+        raise 'Empty title' if title.empty?
+
+        @title = title
+      end
+
+      def src=(src)
+        src = String(src).strip.freeze
+        raise 'Empty src' if src.empty?
+
+        @src = src
+      end
+
+      def url=(url)
+        url = String(url).strip.freeze
+        raise 'Empty url' if url.empty?
+
+        @url = url
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/joint.rb b/lib/repubmark/elems/joint.rb
new file mode 100644
index 0000000..93bfe88
--- /dev/null
+++ b/lib/repubmark/elems/joint.rb
@@ -0,0 +1,170 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Joint < Base
+      parents :Caption, :Quote
+
+      def initialize(parent)
+        super parent
+
+        @raw1   = nil
+        @base   = nil
+        @raw2   = nil
+        @notes  = []
+        @raw3   = nil
+
+        @context = nil
+        @context_note = false
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = components.sum(&:word_count)
+
+      def to_html = components.map(&:to_html).join.freeze
+
+      def to_gemtext = components.map(&:to_gemtext).join.freeze
+
+      ########################
+      # Builder methods: Raw #
+      ########################
+
+      def raw(str)
+        text = Text.new self, str
+        if @notes.any?
+          raise 'Joint raw text already exists' if @raw3
+
+          @raw3 = text
+        elsif @base
+          raise 'Joint raw text already exists' if @raw2
+
+          @raw2 = text
+        else
+          raise 'Joint raw text already exists' if @raw1
+
+          @raw1 = text
+        end
+      end
+
+      #########################
+      # Builder methods: Base #
+      #########################
+
+      def abbrev(abbrev, transcript) = base Abbrev.new self, abbrev, transcript
+
+      def bold(str) = base Text.new self, str, bold: true
+
+      def code_inline(str) = base CodeInline.new self, str
+
+      def ellipsis = base Special.new self, :ellipsis
+
+      def fraction(top, bottom) = base Fraction.new self, top, bottom
+
+      def italic(str) = base Text.new self, str, italic: true
+
+      def link(text, uri) = base Link.new self, text, uri
+
+      def link_italic(text, uri) = base Link.new self, text, uri, italic: true
+
+      def mdash = base Special.new self, :mdash
+
+      def quote(str = nil)
+        quote = Quote.new self
+        case [!!str, block_given?]
+        when [true, false] then quote.text str
+        when [false, true] then yield quote
+        else
+          raise 'Invalid args'
+        end
+        base quote
+      end
+
+      def quote_italic(str)
+        quote = Quote.new self
+        quote.italic str
+        base quote
+      end
+
+      def section(*args) = base Section.new self, *args
+
+      def text(str) = base Text.new self, str
+
+      ##########################
+      # Builder methods: Notes #
+      ##########################
+
+      def context(index, anchor)
+        raise 'Context already given' if @context
+
+        @context = [index, anchor]
+        nil
+      end
+
+      def context_note
+        raise 'No context given' if @context.nil?
+        raise 'Context already noted' if @context_note
+
+        @context_note = true
+        ref_note(*@context)
+      end
+
+      def ref_note(index, anchor)
+        note Note.new self, index, anchor
+      end
+
+    private
+
+      def components
+        raise 'No context note' if @context && !@context_note
+
+        [@raw1, @base, @raw2, *@notes, @raw3].compact
+      end
+
+      def base(elem)
+        raise 'Joint base already exists'   if @base
+        raise 'Joint notes already exist'   if @notes.any?
+
+        @base = elem
+        nil
+      end
+
+      def note(elem)
+        raise 'Joint base does not exists' if @base.nil?
+
+        @notes << elem
+        nil
+      end
+
+      module ForwardingBuilders
+        def joint = raise NotImplementedError, "#{self.class}#joint"
+
+        def abbrev(*args) = joint { |joint| joint.abbrev(*args) }
+
+        def bold(*args) = joint { |joint| joint.bold(*args) }
+
+        def code_inline(*args) = joint { |joint| joint.code_inline(*args) }
+
+        def ellipsis(*args) = joint { |joint| joint.ellipsis(*args) }
+
+        def fraction(*args) = joint { |joint| joint.fraction(*args) }
+
+        def italic(*args) = joint { |joint| joint.italic(*args) }
+
+        def link(*args) = joint { |joint| joint.link(*args) }
+
+        def link_italic(*args) = joint { |joint| joint.link_italic(*args) }
+
+        def mdash(*args) = joint { |joint| joint.mdash(*args) }
+
+        def quote_italic(*args) = joint { |joint| joint.quote_italic(*args) }
+
+        def section(*args) = joint { |joint| joint.section(*args) }
+
+        def text(*args) = joint { |joint| joint.text(*args) }
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/link.rb b/lib/repubmark/elems/link.rb
new file mode 100644
index 0000000..df306d2
--- /dev/null
+++ b/lib/repubmark/elems/link.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Link < Text
+      parents :Joint
+
+      SCHEMES = %w[http https].freeze
+
+      def initialize(parent, str, uri, **kwargs)
+        super parent, str, **kwargs
+
+        self.uri = uri
+        validate_uri!
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html
+        "<a href=\"#{build_uri('.html')}\">#{str_to_html}</a>".freeze
+      end
+
+    private
+
+      attr_reader :uri
+
+      def uri=(uri)
+        @uri = URI.parse(uri).freeze
+      end
+
+      def validate_uri!
+        raise 'Expected normalized URI' unless uri.normalize == uri
+        raise 'Expected no userinfo'    unless uri.userinfo.nil?
+
+        validate_uri_http_absolute!
+      end
+
+      def validate_uri_http_absolute!
+        return unless uri.is_a?(URI::HTTP) && uri.absolute?
+
+        raise 'Invalid scheme'    unless SCHEMES.include? uri.scheme
+        raise 'Expected hostname' unless uri.hostname
+      end
+
+      def build_uri(ext)
+        if uri.is_a?(URI::MailTo) || uri.absolute?
+          uri
+        else
+          own_url "#{uri}#{ext}"
+        end.to_s.freeze
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/list.rb b/lib/repubmark/elems/list.rb
new file mode 100644
index 0000000..9b42a45
--- /dev/null
+++ b/lib/repubmark/elems/list.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class List < Base
+      parents :Canvas, :ListItem
+
+      def initialize(parent, links:, ordered:)
+        super parent
+
+        @links = !!links
+        @ordered = !!ordered
+
+        @items = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @items.sum(&:word_count)
+
+      def to_html
+        [
+          "<#{tag_name}>\n",
+          *@items.map(&:to_html),
+          "</#{tag_name}>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext = @items.map(&:to_gemtext).join
+
+      ##################
+      # Helper methods #
+      ##################
+
+      def level = parent.instance_of?(ListItem) ? parent.level + 1 : 0
+
+      def items_count = @items.count
+
+      def unicode_decor
+        return if level <= 1
+
+        "#{parent.unicode_decor_parent}#{parent.last? ? '⠀ ' : '│ '}"
+      end
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def item(...) = @links ? item_links(...) : item_nolinks(...)
+
+    private
+
+      def parent=(parent)
+        unless parent.instance_of?(Canvas) || parent.instance_of?(ListItem)
+          raise TypeError,
+                "Expected #{Canvas} or #{ListItem}, got #{parent.class}"
+        end
+
+        @parent = parent
+      end
+
+      def tag_name = @ordered ? 'ol' : 'ul'
+
+      def item_nolinks
+        list_item = ListItem.new self, @items.count
+        @items << list_item
+        yield list_item
+        nil
+      end
+
+      def item_links(ref_url, ref_title = nil)
+        titled_ref = TitledRef.new ref_url, ref_title
+        list_item = ListItem.new self, @items.count, titled_ref
+        @items << list_item
+        yield list_item if block_given?
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/list_item.rb b/lib/repubmark/elems/list_item.rb
new file mode 100644
index 0000000..9b73dd3
--- /dev/null
+++ b/lib/repubmark/elems/list_item.rb
@@ -0,0 +1,140 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class ListItem < Base
+      extend Forwardable
+
+      parents :List
+
+      attr_reader :index, :titled_ref
+
+      def initialize(parent, index, titled_ref = nil)
+        super parent
+
+        self.index = index
+        self.titled_ref = titled_ref
+
+        @caption = Caption.new self
+        @sublist = nil
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @caption.word_count + (@sublist&.word_count || 0)
+
+      def to_html
+        [
+          "<li>\n",
+          build_ref(:html),
+          @caption.to_html,
+          @sublist&.to_html,
+          "</li>\n",
+        ].join.freeze
+      end
+
+      def to_gemtext
+        [
+          if titled_ref
+            "#{build_ref(:gemtext)}#{@caption.to_gemtext}".strip
+          else
+            "* #{unicode_decor_own}#{@caption.to_gemtext}".strip
+          end,
+          @sublist&.to_gemtext,
+        ].join("\n").freeze
+      end
+
+      ##################
+      # Helper methods #
+      ##################
+
+      def level = parent.level
+
+      def last? = index >= parent.items_count - 1
+
+      def unicode_decor_own
+        "#{parent.unicode_decor}#{last? ? '└' : '├'} " unless level.zero?
+      end
+
+      def unicode_decor_parent = parent.unicode_decor
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def subolist
+        raise 'No nested link lists' if titled_ref
+        raise 'Sublist already exists' if @sublist
+
+        @sublist = List.new self, links: false, ordered: true
+        yield @sublist
+        nil
+      end
+
+      def subulist
+        raise 'No nested link lists' if titled_ref
+        raise 'Sublist already exists' if @sublist
+
+        @sublist = List.new self, links: false, ordered: false
+        yield @sublist
+        nil
+      end
+
+      def respond_to_missing?(method_name, _include_private)
+        @caption.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @caption.respond_to? method_name
+          raise 'Caption after sublist' if @sublist
+
+          @caption.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+
+    private
+
+      def parent=(parent)
+        unless parent.instance_of? List
+          raise TypeError, "Expected #{List}, got #{parent.class}"
+        end
+
+        @parent = parent
+      end
+
+      def index=(index)
+        index = Integer index
+        raise 'Invalid index' if index.negative?
+
+        @index = index
+      end
+
+      def titled_ref=(titled_ref)
+        return @titled_ref = nil if titled_ref.nil?
+
+        unless titled_ref.instance_of? TitledRef
+          raise TypeError, "Expected #{TitledRef}, got #{titled_ref.class}"
+        end
+
+        @titled_ref = titled_ref
+      end
+
+      def build_ref(format)
+        return if titled_ref.nil?
+
+        case format
+        when :html
+          "<a href=\"#{titled_ref.url}\">#{titled_ref.title}</a>\n".freeze
+        when :gemtext
+          "=> #{titled_ref.url} #{unicode_decor_own}#{titled_ref.title} ".freeze
+        else
+          raise 'Invalid format'
+        end
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/note.rb b/lib/repubmark/elems/note.rb
new file mode 100644
index 0000000..9d268db
--- /dev/null
+++ b/lib/repubmark/elems/note.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Note < Base
+      parents :Joint
+
+      UNICODE_SUPS = {
+        '1' => '¹',
+        '2' => '²',
+        '3' => '³',
+        '4' => '⁴',
+        '5' => '⁵',
+        '6' => '⁶',
+        '7' => '⁷',
+        '8' => '⁸',
+        '9' => '⁹',
+        '0' => '⁰',
+      }.freeze
+
+      def initialize(parent, index, anchor)
+        super parent
+        @index = index
+        @anchor = anchor
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html
+        [
+          '<sup>',
+          %(<a href="##{CGI.escape_html(@anchor)}">),
+          %([#{CGI.escape_html(@index.to_s)}]),
+          '</a>',
+          '</sup>',
+        ].join.freeze
+      end
+
+      def to_gemtext = "⁽#{index_unicode_sup}⁾".freeze
+
+    private
+
+      def index_unicode_sup
+        @index_unicode_sup ||=
+          @index.to_s.each_char.map { |chr| UNICODE_SUPS.fetch chr }.join.freeze
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/paragraph.rb b/lib/repubmark/elems/paragraph.rb
new file mode 100644
index 0000000..9b46cd7
--- /dev/null
+++ b/lib/repubmark/elems/paragraph.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Paragraph < Base
+      parents :Canvas
+
+      def initialize(parent)
+        super parent
+        @caption = Caption.new self
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @caption.word_count
+
+      def to_html = "<p>\n#{@caption.to_html}</p>\n".freeze
+
+      def to_gemtext = "#{@caption.to_gemtext}\n".freeze
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def respond_to_missing?(method_name, _include_private)
+        @caption.respond_to?(method_name) || super
+      end
+
+      def method_missing(method_name, ...)
+        if @caption.respond_to?(method_name)
+          @caption.public_send(method_name, ...)
+        else
+          super
+        end
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/quote.rb b/lib/repubmark/elems/quote.rb
new file mode 100644
index 0000000..bb685d4
--- /dev/null
+++ b/lib/repubmark/elems/quote.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Quote < Base
+      include Joint::ForwardingBuilders
+
+      parents :Caption, :Joint, :Quote
+
+      def initialize(...)
+        super
+        @items = []
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = @items.sum(&:word_count)
+
+      def to_html = "&laquo;#{@items.map(&:to_html).join("\n")}&raquo;".freeze
+
+      def to_gemtext = "«#{@items.map(&:to_gemtext).join(' ')}»".freeze
+
+      ###################
+      # Builder methods #
+      ###################
+
+      def joint
+        joint = Joint.new self
+        yield joint
+        @items << joint
+        nil
+      end
+
+      def quote(str = nil)
+        quote = Quote.new self
+        case [!!str, block_given?]
+        when [true, false] then quote.text str
+        when [false, true] then yield quote
+        else
+          raise 'Invalid args'
+        end
+        @items << quote
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/section.rb b/lib/repubmark/elems/section.rb
new file mode 100644
index 0000000..02ac611
--- /dev/null
+++ b/lib/repubmark/elems/section.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Section < Base
+      parents :Joint
+
+      SECT_HTML = '&sect;'
+      SECT_GEMTEXT = '§'
+
+      attr_reader :count, :text
+
+      def initialize(parent, *args)
+        super parent
+
+        case args.length
+        when 1
+          self.count = 1
+          self.text = args[0]
+        when 2
+          self.count, self.text = args
+        else
+          raise ArgumentError, 'Expected 1 or 2 arguments'
+        end
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = count_words @text
+
+      def to_html = "#{SECT_HTML * count}#{text}".freeze
+
+      def to_gemtext = "#{SECT_GEMTEXT * count}#{text}".freeze
+
+    private
+
+      def count=(count)
+        unless count.instance_of? Integer
+          raise TypeError, "Expected #{Integer}, got #{count.class}"
+        end
+        raise 'Expected positive count' unless count.positive?
+
+        @count = count
+      end
+
+      def text=(text)
+        text = String(text).strip.freeze
+        raise 'Expected non-empty text' if text.empty?
+
+        @text = text
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/elems/separator.rb b/lib/repubmark/elems/separator.rb
new file mode 100644
index 0000000..a686699
--- /dev/null
+++ b/lib/repubmark/elems/separator.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Separator < Base
+      parents :Canvas
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html = "<hr/>\n"
+
+      def to_gemtext = "---\n"
+    end
+  end
+end
diff --git a/lib/repubmark/elems/special.rb b/lib/repubmark/elems/special.rb
new file mode 100644
index 0000000..eb1c2e3
--- /dev/null
+++ b/lib/repubmark/elems/special.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    # TODO: maybe don't allow mdash everywhere
+    class Special < Base
+      parents :Joint
+
+      HTML = {
+        ellipsis: '&hellip;',
+        mdash: '&mdash;',
+      }.freeze
+
+      GEMTEXT = {
+        ellipsis: '…',
+        mdash: '—',
+      }.freeze
+
+      def initialize(parent, name)
+        super parent
+        name = String(name).to_sym.freeze
+        HTML.fetch name
+        @name = name
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def to_html = HTML.fetch @name
+
+      def to_gemtext = GEMTEXT.fetch @name
+    end
+  end
+end
diff --git a/lib/repubmark/elems/text.rb b/lib/repubmark/elems/text.rb
new file mode 100644
index 0000000..827971e
--- /dev/null
+++ b/lib/repubmark/elems/text.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module Repubmark
+  module Elems
+    class Text < Base
+      parents :Joint
+
+      def initialize(parent, str, bold: false, italic: false)
+        super parent
+
+        self.str = str
+
+        @bold   = !!bold
+        @italic = !!italic
+      end
+
+      #################
+      # Basic methods #
+      #################
+
+      def word_count = count_words @str
+
+      def to_html = str_to_html
+
+      def to_gemtext = @str
+
+    private
+
+      def str=(str)
+        @str = String(str).split.join(' ').freeze
+      end
+
+      def str_to_html
+        result = @str
+        result = "<em>#{result}</em>"         if @italic
+        result = "<strong>#{result}</strong>" if @bold
+        result.freeze
+      end
+    end
+  end
+end
diff --git a/lib/repubmark/highlight.rb b/lib/repubmark/highlight.rb
new file mode 100644
index 0000000..f4bbb4d
--- /dev/null
+++ b/lib/repubmark/highlight.rb
@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+module Repubmark
+  class Highlight
+    NO_SYNTAX = 'txt'
+
+    NO_LINE_NUMBERS = %i[sh_hist].freeze
+
+    SYNTAXES = {
+      certbot: 'ini',
+      css: 'css',
+      hjson: nil,
+      html: 'html',
+      ini: 'ini',
+      knockd: nil,
+      nginx: 'nginx',
+      openssh: nil,
+      ruby: 'ruby',
+      sh_hist: nil,
+      sysctl: nil,
+      torrc: nil,
+      wireguard: 'ini',
+      yggdrasil: nil, # Hjson
+    }.freeze
+
+    private_class_method :new
+
+    def self.call(...) = new(...).call
+
+    attr_reader :syntax, :str
+
+    def initialize(syntax, str)
+      self.syntax = syntax
+      self.str = str
+    end
+
+    def call
+      Open3.popen2(*cmdline) do |stdin, stdout, wait_thr|
+        stdin.write str
+        stdin.close
+        result = stdout.read.freeze
+        raise 'Highlight error' unless wait_thr.value.success?
+
+        "<pre><code>#{result}</code></pre>\n".freeze
+      end
+    end
+
+  private
+
+    def syntax=(syntax)
+      return @syntax = nil if syntax.nil?
+
+      unless syntax.instance_of? Symbol
+        raise TypeError, "Expected #{Symbol}, got #{syntax.class}"
+      end
+
+      SYNTAXES.fetch syntax
+
+      @syntax = syntax
+    end
+
+    def str=(str)
+      str = String(str).strip.freeze
+      raise 'Expected non-empty string' if str.empty?
+
+      @str = str
+    end
+
+    def cmdline
+      @cmdline ||= [
+        'highlight',
+        '--stdout',
+        '--fragment',
+        '--out-format',
+        'html',
+        '--syntax',
+        SYNTAXES[syntax] || NO_SYNTAX,
+      ].tap do |cmdline|
+        unless syntax.nil? || NO_LINE_NUMBERS.include?(syntax)
+          cmdline << '--line-numbers'
+        end
+      end.freeze
+    end
+  end
+end
diff --git a/lib/repubmark/setup.rb b/lib/repubmark/setup.rb
new file mode 100644
index 0000000..ac9af0e
--- /dev/null
+++ b/lib/repubmark/setup.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Repubmark
+  class Setup
+    def initialize(**kwargs)
+      kwargs.each { |key, value| public_send :"#{key}=", value }
+      yield self if block_given?
+      freeze
+    end
+
+    attr_reader :prologue, :epilogue
+
+    def prologue=(prologue)
+      prologue = String(prologue).strip.freeze
+      prologue = nil if prologue.empty?
+      @prologue = prologue
+    end
+
+    def epilogue=(epilogue)
+      epilogue = String(epilogue).strip.freeze
+      epilogue = nil if epilogue.empty?
+      @epilogue = epilogue
+    end
+
+    ##########
+    # Locale #
+    ##########
+
+    LOCALE_RE = /\A[a-z]{2,3}\z/
+    DEFAULT_LOCALE = :en
+
+    def locale = @locale || DEFAULT_LOCALE
+
+    def locale=(locale)
+      locale = String(locale).to_sym
+      raise 'Invalid locale' unless LOCALE_RE.match? locale
+      raise 'Locale has already been set' if @locale
+
+      @locale = locale
+    end
+  end
+end
diff --git a/lib/repubmark/titled_ref.rb b/lib/repubmark/titled_ref.rb
new file mode 100644
index 0000000..bda0e1b
--- /dev/null
+++ b/lib/repubmark/titled_ref.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Repubmark
+  class TitledRef
+    attr_reader :url, :title
+
+    def initialize(url, title)
+      self.url = url
+      self.title = title
+    end
+
+  private
+
+    attr_writer :url, :title
+  end
+end