diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..c2fc528
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,29 @@
+# The behavior of RuboCop can be controlled via the .rubocop.yml
+# configuration file. It makes it possible to enable/disable
+# certain cops (checks) and to alter their behavior if they accept
+# any parameters. The file can be placed either in your home
+# directory or in some project directory.
+#
+# RuboCop will start looking for the configuration file in the directory
+# where the inspected file is and continue its way up to the root directory.
+#
+# See https://github.com/rubocop-hq/rubocop/blob/master/manual/configuration.md
+
+Layout/LineLength:
+  Max: 120
+
+Style/HashEachMethods:
+  Enabled: true
+
+Style/HashTransformKeys:
+  Enabled: true
+
+Style/HashTransformValues:
+  Enabled: true
+
+Metrics/BlockLength:
+  Exclude:
+    - spec/**/*_spec.rb
+
+Style/Documentation:
+  Enabled: false
diff --git a/Gemfile b/Gemfile
index a09dc13..6bfa264 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,6 +5,7 @@ source 'https://rubygems.org'
 # Specify your gem's dependencies in wag.gemspec
 gemspec
 
+gem 'pry', '~> 0.13.0'
 gem 'rake', '~> 12.0'
 gem 'rspec', '~> 3.0'
 gem 'rubocop', '~> 0.80.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index d041131..08d1876 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,16 +2,23 @@ PATH
   remote: .
   specs:
     wag (0.1.0)
+      dry-inflector (~> 0.2.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
     ast (2.4.0)
+    coderay (1.1.2)
     diff-lcs (1.3)
+    dry-inflector (0.2.0)
     jaro_winkler (1.5.4)
+    method_source (1.0.0)
     parallel (1.19.1)
     parser (2.7.0.5)
       ast (~> 2.4.0)
+    pry (0.13.0)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
     rainbow (3.0.0)
     rake (12.3.3)
     rexml (3.2.4)
@@ -43,6 +50,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  pry (~> 0.13.0)
   rake (~> 12.0)
   rspec (~> 3.0)
   rubocop (~> 0.80.1)
diff --git a/README.md b/README.md
index 6287e3e..591e246 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,24 @@
-# Wag
+# WAG - The WebAssembly Code Generator
 
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/wag`. To experiment with that code, run `bin/console` for an interactive prompt.
+This Ruby gem allows you to generate WebAssembly programs programatically.
 
-TODO: Delete this and the text above, and describe your gem
+## Example
+
+```ruby
+WAG::Module.new.build do
+  memory(1)
+  export('memory', :memory)
+  export('hello', :$hello)
+  func(:$hello) do
+    result(:i32)
+    i32.const(16)
+  end
+  data do
+    i32.const(16)
+    << "Hello World\00"
+  end
+end
+```
 
 ## Installation
 
diff --git a/lib/wag.rb b/lib/wag.rb
index 2f02816..27c98b2 100644
--- a/lib/wag.rb
+++ b/lib/wag.rb
@@ -2,7 +2,25 @@
 
 require 'wag/version'
 
-module Wag
+module WAG
   class Error < StandardError; end
   # Your code goes here...
+
+  require 'wag/wat'
+
+  require 'wag/data'
+  require 'wag/function'
+  require 'wag/function_type'
+  require 'wag/global'
+  require 'wag/element'
+  require 'wag/export'
+  require 'wag/import'
+  require 'wag/indices'
+  require 'wag/inflector'
+  require 'wag/instruction'
+  require 'wag/label'
+  require 'wag/memory'
+  require 'wag/module'
+  require 'wag/table'
+  require 'wag/type'
 end
diff --git a/lib/wag/data.rb b/lib/wag/data.rb
new file mode 100644
index 0000000..ab15727
--- /dev/null
+++ b/lib/wag/data.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module WAG
+  class Data
+    include WAG::WAT
+
+    attr_reader :offset, :value
+
+    def initialize(offset, value)
+      @offset = offset.to_i
+      @value = value
+    end
+
+    def to_sexpr
+      [:data, [:"i32.const", offset], value]
+    end
+  end
+end
diff --git a/lib/wag/element.rb b/lib/wag/element.rb
new file mode 100644
index 0000000..48fc59e
--- /dev/null
+++ b/lib/wag/element.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module WAG
+  class Element
+    include WAG::WAT
+
+    attr_reader :table_id, :labels
+
+    def initialize(table_id, *labels)
+      @table_id = table_id.to_i
+      @labels = labels.map { |l| WAG::Label.from(l) }
+    end
+
+    def to_sexpr
+      [:elem, [:"i32.const", table_id]].concat(labels.map(&:to_sexpr))
+    end
+  end
+end
diff --git a/lib/wag/export.rb b/lib/wag/export.rb
new file mode 100644
index 0000000..499a21c
--- /dev/null
+++ b/lib/wag/export.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module WAG
+  class Export
+    include WAG::WAT
+
+    attr_reader :name, :desc
+
+    def initialize(name)
+      @name = name
+    end
+
+    def func(label, &block)
+      @desc = Function.new(label)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def global(label, type)
+      @desc = Global.new(label, type)
+    end
+
+    def memory(number, min: nil, max: nil, &block)
+      @desc = Memory.new(number, min: min, max: max)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def table(number, type = :funcref, min: nil, max: nil, &block)
+      @desc = Table.new(number, type, min: min, max: max)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def to_sexpr
+      [:export, name, desc.to_sexpr]
+    end
+  end
+end
diff --git a/lib/wag/function.rb b/lib/wag/function.rb
new file mode 100644
index 0000000..091bc4a
--- /dev/null
+++ b/lib/wag/function.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module WAG
+  class Function
+    include WAG::WAT
+
+    attr_reader :label, :params, :results
+
+    def initialize(label)
+      @label = WAG::Label.from(label)
+      @params = []
+      @results = []
+    end
+
+    def param(*types)
+      @params.concat(types.map { |t| WAG::Type.from(t) })
+    end
+
+    def result(*types)
+      @results.concat(types.map { |t| WAG::Type.from(t) })
+    end
+
+    def to_sexpr
+      [:func, @label.to_sexpr].tap do |func|
+        func.push([:param].concat(@params.map(&:to_sexpr))) if @params
+        func.push([:result].concat(@results.map(&:to_sexpr))) if @results
+      end
+    end
+  end
+end
diff --git a/lib/wag/function_type.rb b/lib/wag/function_type.rb
new file mode 100644
index 0000000..3954ed5
--- /dev/null
+++ b/lib/wag/function_type.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module WAG
+  class FunctionType
+    include WAG::WAT
+
+    attr_reader :label, :params, :results
+
+    def initialize(label)
+      @label = WAG::Label.from(label)
+      @params = []
+      @results = []
+    end
+
+    def param(*types)
+      @params.concat(types.map { |t| WAG::Type.from(t) })
+    end
+
+    def result(*types)
+      @results.concat(types.map { |t| WAG::Type.from(t) })
+    end
+
+    def to_sexpr
+      [:type, @label.to_sexpr,
+       [:func].tap do |func|
+         func.push([:param].concat(@params.map(&:to_sexpr))) if @params
+         func.push([:result].concat(@results.map(&:to_sexpr))) if @results
+       end]
+    end
+  end
+end
diff --git a/lib/wag/global.rb b/lib/wag/global.rb
new file mode 100644
index 0000000..dcb2e28
--- /dev/null
+++ b/lib/wag/global.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module WAG
+  class Global
+    include WAG::WAT
+
+    attr_reader :label, :type
+
+    def initialize(label, type)
+      @label = WAG::Label.from(label)
+      @type = WAG::Type.from(type)
+    end
+
+    def to_sexpr
+      [:global, label.to_sexpr, type.to_sexpr]
+    end
+  end
+end
diff --git a/lib/wag/import.rb b/lib/wag/import.rb
new file mode 100644
index 0000000..81fbd4f
--- /dev/null
+++ b/lib/wag/import.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module WAG
+  class Import
+    include WAG::WAT
+
+    attr_reader :module_name, :name, :desc
+
+    def initialize(module_name, name)
+      @module_name = module_name
+      @name = name
+    end
+
+    def func(label, &block)
+      @desc = Function.new(label)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def global(label, type, &block)
+      @desc = Global.new(label, type)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def memory(number, min: nil, max: nil, &block)
+      @desc = Memory.new(number, min: min, max: max)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def table(number, type = :funcref, min: nil, max: nil, &block)
+      @desc = Table.new(number, type, min: min, max: max)
+      @desc.instance_exec(&block) if block
+      @desc
+    end
+
+    def to_sexpr
+      [:import, module_name, name, desc.to_sexpr]
+    end
+  end
+end
diff --git a/lib/wag/indices.rb b/lib/wag/indices.rb
new file mode 100644
index 0000000..e2ba6ab
--- /dev/null
+++ b/lib/wag/indices.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    require 'wag/indices/base'
+    require 'wag/indices/func'
+    require 'wag/indices/global'
+    require 'wag/indices/label'
+    require 'wag/indices/local'
+    require 'wag/indices/mem'
+    require 'wag/indices/table'
+    require 'wag/indices/type'
+  end
+end
diff --git a/lib/wag/indices/base.rb b/lib/wag/indices/base.rb
new file mode 100644
index 0000000..40dc5ab
--- /dev/null
+++ b/lib/wag/indices/base.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Base
+      RANGE = [0..0xFFFFFFFF].freeze
+      attr_reader :value
+
+      def initialize(value)
+        raise "Index 0x#{value.to_s(16)} does not fit in an i32" unless RANGE.cover?(value)
+
+        @value = value
+      end
+    end
+  end
+end
diff --git a/lib/wag/indices/func.rb b/lib/wag/indices/func.rb
new file mode 100644
index 0000000..4baec58
--- /dev/null
+++ b/lib/wag/indices/func.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Func < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/global.rb b/lib/wag/indices/global.rb
new file mode 100644
index 0000000..0403a2e
--- /dev/null
+++ b/lib/wag/indices/global.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Global < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/label.rb b/lib/wag/indices/label.rb
new file mode 100644
index 0000000..03b7ef1
--- /dev/null
+++ b/lib/wag/indices/label.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Label < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/local.rb b/lib/wag/indices/local.rb
new file mode 100644
index 0000000..6d3bea1
--- /dev/null
+++ b/lib/wag/indices/local.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Local < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/mem.rb b/lib/wag/indices/mem.rb
new file mode 100644
index 0000000..5a5bf2e
--- /dev/null
+++ b/lib/wag/indices/mem.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Mem < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/table.rb b/lib/wag/indices/table.rb
new file mode 100644
index 0000000..b4abcd1
--- /dev/null
+++ b/lib/wag/indices/table.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Table < Base
+    end
+  end
+end
diff --git a/lib/wag/indices/type.rb b/lib/wag/indices/type.rb
new file mode 100644
index 0000000..650d908
--- /dev/null
+++ b/lib/wag/indices/type.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Indices
+    class Type < Base
+    end
+  end
+end
diff --git a/lib/wag/inflector.rb b/lib/wag/inflector.rb
new file mode 100644
index 0000000..5e4a96b
--- /dev/null
+++ b/lib/wag/inflector.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require 'dry-inflector'
+
+module WAG
+  module Inflector
+    module_function
+
+    def inflector
+      @inflector ||= Dry::Inflector.new
+    end
+  end
+end
diff --git a/lib/wag/instruction.rb b/lib/wag/instruction.rb
new file mode 100644
index 0000000..b2e1bbf
--- /dev/null
+++ b/lib/wag/instruction.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    require 'wag/instructions/base'
+
+    require 'wag/instructions/block'
+    require 'wag/instructions/br_if'
+    require 'wag/instructions/br_table'
+    require 'wag/instructions/br'
+    require 'wag/instructions/else'
+    require 'wag/instructions/end'
+    require 'wag/instructions/if'
+    require 'wag/instructions/loop'
+    require 'wag/instructions/nop'
+    require 'wag/instructions/return'
+    require 'wag/instructions/unreachable'
+  end
+end
diff --git a/lib/wag/instructions/base.rb b/lib/wag/instructions/base.rb
new file mode 100644
index 0000000..0445d2c
--- /dev/null
+++ b/lib/wag/instructions/base.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Base
+      include WAG::WAT
+
+      def self.instruction(op_code)
+        klass = Class.new(WAG::Instruction::Base)
+        klass.define_method(:op_code) { op_code }
+        klass
+      end
+
+      def name
+        name = WAG::Inflector.inflector.demodulize(self.class.name.to_s)
+        WAG::Inflector.inflector.underscore(name).to_sym
+      end
+
+      def to_sexpr
+        name.to_sym
+      end
+    end
+  end
+end
diff --git a/lib/wag/instructions/block.rb b/lib/wag/instructions/block.rb
new file mode 100644
index 0000000..34eab72
--- /dev/null
+++ b/lib/wag/instructions/block.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Block < Base.instruction(0x02)
+    end
+  end
+end
diff --git a/lib/wag/instructions/br.rb b/lib/wag/instructions/br.rb
new file mode 100644
index 0000000..097e676
--- /dev/null
+++ b/lib/wag/instructions/br.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Br < Base.instruction(0x0c)
+      attr_reader :label
+
+      def initialize(label)
+        @label = WAG::Label.from(label)
+      end
+
+      def to_sexpr
+        [name, label.to_sexpr]
+      end
+    end
+  end
+end
diff --git a/lib/wag/instructions/br_if.rb b/lib/wag/instructions/br_if.rb
new file mode 100644
index 0000000..168e0b0
--- /dev/null
+++ b/lib/wag/instructions/br_if.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class BrIf < Base.instruction(0x0d)
+      attr_reader :label
+
+      def initialize(label)
+        @label = WAG::Label.from(label)
+      end
+
+      def to_sexpr
+        [name, label.to_sexpr]
+      end
+    end
+  end
+end
diff --git a/lib/wag/instructions/br_table.rb b/lib/wag/instructions/br_table.rb
new file mode 100644
index 0000000..a8252d4
--- /dev/null
+++ b/lib/wag/instructions/br_table.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class BrTable < Base.instruction(0x0e)
+      attr_reader :label
+
+      def initialize(*labels)
+        @labels = labels.map { |label| WAG::Label.from(label) }
+      end
+
+      def to_sexpr
+        [name].concat(@labels.map(&:to_sexpr))
+      end
+    end
+  end
+end
diff --git a/lib/wag/instructions/else.rb b/lib/wag/instructions/else.rb
new file mode 100644
index 0000000..0d0bce9
--- /dev/null
+++ b/lib/wag/instructions/else.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Else < Base.instruction(0x05)
+    end
+  end
+end
diff --git a/lib/wag/instructions/end.rb b/lib/wag/instructions/end.rb
new file mode 100644
index 0000000..f3d5148
--- /dev/null
+++ b/lib/wag/instructions/end.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class End < Base.instruction(0x0b)
+    end
+  end
+end
diff --git a/lib/wag/instructions/if.rb b/lib/wag/instructions/if.rb
new file mode 100644
index 0000000..9509da9
--- /dev/null
+++ b/lib/wag/instructions/if.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class If < Base.instruction(0x04)
+    end
+  end
+end
diff --git a/lib/wag/instructions/loop.rb b/lib/wag/instructions/loop.rb
new file mode 100644
index 0000000..3ad000e
--- /dev/null
+++ b/lib/wag/instructions/loop.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Loop < Base.instruction(0x03)
+    end
+  end
+end
diff --git a/lib/wag/instructions/nop.rb b/lib/wag/instructions/nop.rb
new file mode 100644
index 0000000..0860ab3
--- /dev/null
+++ b/lib/wag/instructions/nop.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Nop < Base.instruction(0x01)
+    end
+  end
+end
diff --git a/lib/wag/instructions/return.rb b/lib/wag/instructions/return.rb
new file mode 100644
index 0000000..7c43a2a
--- /dev/null
+++ b/lib/wag/instructions/return.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Return < Base.instruction(0x0f)
+    end
+  end
+end
diff --git a/lib/wag/instructions/unreachable.rb b/lib/wag/instructions/unreachable.rb
new file mode 100644
index 0000000..d153371
--- /dev/null
+++ b/lib/wag/instructions/unreachable.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Instruction
+    class Unreachable < Base.instruction(0x00)
+    end
+  end
+end
diff --git a/lib/wag/label.rb b/lib/wag/label.rb
new file mode 100644
index 0000000..6381b7b
--- /dev/null
+++ b/lib/wag/label.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module WAG
+  class Label
+    include WAG::WAT
+
+    attr_reader :value
+
+    def initialize(value)
+      @value = value.to_s
+      @value = @value[1..-1] if @value.start_with?('$')
+    end
+
+    def to_sexpr
+      "$#{value}".to_sym
+    end
+
+    def self.from(value)
+      return value if value.is_a?(WAG::Label)
+
+      WAG::Label.new(value)
+    end
+  end
+end
diff --git a/lib/wag/memory.rb b/lib/wag/memory.rb
new file mode 100644
index 0000000..c545d02
--- /dev/null
+++ b/lib/wag/memory.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module WAG
+  class Memory
+    include WAG::WAT
+
+    attr_reader :number, :min, :max
+
+    def initialize(number, min: nil, max: nil)
+      @number = number
+      @min = min
+      @max = max
+    end
+
+    def to_sexpr
+      wat = [:memory, number]
+
+      wat.concat([:min, min]) if min
+      wat.concat([:max, max]) if max
+
+      wat
+    end
+  end
+end
diff --git a/lib/wag/module.rb b/lib/wag/module.rb
new file mode 100644
index 0000000..02b4feb
--- /dev/null
+++ b/lib/wag/module.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+module WAG
+  class Module
+    include WAG::WAT
+
+    def initialize
+      @data = []
+      @elements = []
+      @exports = []
+      @functions = []
+      @globals = []
+      @imports = []
+      @memories = []
+      @types = []
+    end
+
+    def import(module_name, name, &block)
+      import = Import.new(module_name, name)
+      @imports << import
+      import.instance_exec(&block) if block
+      import
+    end
+
+    def export(name, &block)
+      export = Export.new(name)
+      @exports << export
+      export.instance_exec(&block) if block
+      export
+    end
+
+    def memory(number, min: nil, max: nil, &block)
+      mem = Memory.new(number, min: min, max: max)
+      @memories << mem
+      mem.instance_exec(&block) if block
+      mem
+    end
+
+    def global(label, type, &block)
+      global = Global.new(label, type)
+      @globals << global
+      global.instance_exec(&block) if block
+      global
+    end
+
+    def type(label, &block)
+      type = FunctionType.new(label)
+      @types << type
+      type.instance_exec(&block) if block
+      type
+    end
+
+    def elem(table_id, *labels, &block)
+      elem = Element.new(table_id, *labels)
+      @elements << elem
+      elem.instance_exec(&block) if block
+      elem
+    end
+
+    def data(offset, value, &block)
+      data = Data.new(offset, value)
+      @data << data
+      data.instance_exec(&block) if block
+      data
+    end
+
+    def func(label, &block)
+      func = Function.new(label)
+      @functions << func
+      func.instance_exec(&block) if block
+      func
+    end
+
+    def to_sexpr # rubocop:disable Metrics/AbcSize
+      mod = [:module]
+      mod.concat(@imports.map(&:to_sexpr))
+      mod.concat(@exports.map(&:to_sexpr))
+      mod.concat(@memories.map(&:to_sexpr))
+      mod.concat(@globals.map(&:to_sexpr))
+      mod.concat(@types.map(&:to_sexpr))
+      mod.concat(@elements.map(&:to_sexpr))
+      mod.concat(@data.map(&:to_sexpr))
+      mod.concat(@functions.map(&:to_sexpr))
+      mod
+    end
+  end
+end
diff --git a/lib/wag/table.rb b/lib/wag/table.rb
new file mode 100644
index 0000000..a577cdf
--- /dev/null
+++ b/lib/wag/table.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module WAG
+  class Table
+    include WAG::WAT
+
+    RANGE = (0..0xFFFFFFFF).freeze
+
+    attr_reader :number, :type, :min, :max
+
+    def initialize(number, type = :funcref, min: nil, max: nil) # rubocop:disable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+      raise '`min` must fit in u32 range' if min && !RANGE.cover?(min)
+      raise '`max` must fit in u32 range' if max && !RANGE.cover?(max)
+      raise '`max` must be greater than `min`' if min && max && min > max
+
+      @number = number
+      @type = type
+      @min = min
+      @max = max
+    end
+
+    def to_sexpr
+      expr = [:table, number, type]
+      expr.concat([:min, min]) if min
+      expr.concat([:max, max]) if max
+      expr
+    end
+  end
+end
diff --git a/lib/wag/type.rb b/lib/wag/type.rb
new file mode 100644
index 0000000..b1f2015
--- /dev/null
+++ b/lib/wag/type.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    require 'wag/types/base'
+    require 'wag/types/i32'
+    require 'wag/types/i64'
+    require 'wag/types/f32'
+    require 'wag/types/f64'
+
+    module_function
+
+    def from(type)
+      return type if type.is_a?(WAG::Type::Base)
+
+      const_get(WAG::Inflector.inflector.camelize(type.to_s)).new
+    end
+  end
+end
diff --git a/lib/wag/types/base.rb b/lib/wag/types/base.rb
new file mode 100644
index 0000000..7653a63
--- /dev/null
+++ b/lib/wag/types/base.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    class Base
+      def to_sexpr
+        name = WAG::Inflector.inflector.demodulize(self.class.name.to_s)
+        WAG::Inflector.inflector.underscore(name).to_sym
+      end
+
+      def value?
+        true
+      end
+    end
+  end
+end
diff --git a/lib/wag/types/f32.rb b/lib/wag/types/f32.rb
new file mode 100644
index 0000000..337b32a
--- /dev/null
+++ b/lib/wag/types/f32.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    class F32 < Base
+    end
+  end
+end
diff --git a/lib/wag/types/f64.rb b/lib/wag/types/f64.rb
new file mode 100644
index 0000000..921acab
--- /dev/null
+++ b/lib/wag/types/f64.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    class F64 < Base
+    end
+  end
+end
diff --git a/lib/wag/types/function.rb b/lib/wag/types/function.rb
new file mode 100644
index 0000000..ee62d37
--- /dev/null
+++ b/lib/wag/types/function.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    # A WebAssembly function type.
+    class Function < Base
+      attr_reader :parameter_types, :return_types
+
+      def initialize(parameter_types, return_types)
+        parameter_types.map! { |t| Huia::Type.from(t) }
+        return_types.map! { |t| Huia::Type.from(t) }
+
+        raise 'There must only be one return type (at the moment)' unless return_types.one?
+
+        unless parameter_types.all?(&:value?) && return_types.all?(&:value?)
+          raise 'Function type parameters can only be value types'
+        end
+
+        @parameter_types = parameter_types
+        @return_types = return_types
+      end
+
+      def value?
+        false
+      end
+    end
+  end
+end
diff --git a/lib/wag/types/i32.rb b/lib/wag/types/i32.rb
new file mode 100644
index 0000000..64860eb
--- /dev/null
+++ b/lib/wag/types/i32.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    class I32 < Base
+    end
+  end
+end
diff --git a/lib/wag/types/i64.rb b/lib/wag/types/i64.rb
new file mode 100644
index 0000000..2bb43f7
--- /dev/null
+++ b/lib/wag/types/i64.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module WAG
+  module Type
+    class I64 < Base
+    end
+  end
+end
diff --git a/lib/wag/version.rb b/lib/wag/version.rb
index 5ee7bc2..286156f 100644
--- a/lib/wag/version.rb
+++ b/lib/wag/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
-module Wag
+module WAG
   VERSION = '0.1.0'
 end
diff --git a/lib/wag/wat.rb b/lib/wag/wat.rb
new file mode 100644
index 0000000..3f35cbc
--- /dev/null
+++ b/lib/wag/wat.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module WAG
+  # A simple mixin which formats s-expressions as WAT.
+  module WAT
+    def to_wat
+      wat_encode(to_sexpr)
+    end
+
+    private
+
+    def wat_encode(data)
+      return "(#{data.map { |e| wat_encode(e) }.join(' ')})" if data.is_a?(Enumerable)
+      return data.inspect if data.is_a?(String)
+
+      data.to_s
+    end
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 1d2c194..c88bf25 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -2,6 +2,7 @@
 
 require 'bundler/setup'
 require 'wag'
+require 'pry'
 
 RSpec.configure do |config|
   # Enable flags like --only-failures and --next-failure
diff --git a/spec/wag/export_spec.rb b/spec/wag/export_spec.rb
new file mode 100644
index 0000000..2cd2455
--- /dev/null
+++ b/spec/wag/export_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe WAG::Export do
+  let(:export) { described_class.new('marty') }
+  subject { export }
+
+  describe 'When exporting memory' do
+    before do
+      export.memory(1, min: 1, max: 64)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:export, 'marty', [:memory, 1, :min, 1, :max, 64]] }
+    end
+  end
+
+  describe 'When exporting a table' do
+    before do
+      export.table(1, :funcref, min: 1, max: 64)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:export, 'marty', [:table, 1, :funcref, :min, 1, :max, 64]] }
+    end
+  end
+
+  describe 'When exporting a function' do
+    before do
+      export.func(:foo) do
+        param(:f32, :f64)
+        result(:i32)
+      end
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:export, 'marty', [:func, :$foo, %i[param f32 f64], %i[result i32]]] }
+    end
+  end
+
+  describe 'When exporting a global' do
+    before do
+      export.global(:foo, :i32)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:export, 'marty', %i[global $foo i32]] }
+    end
+  end
+end
diff --git a/spec/wag/import_spec.rb b/spec/wag/import_spec.rb
new file mode 100644
index 0000000..8a895ae
--- /dev/null
+++ b/spec/wag/import_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe WAG::Import do
+  let(:import) { described_class.new('marty', 'mcfly') }
+  subject { import }
+
+  describe 'When importing memory' do
+    before do
+      import.memory(1, min: 1, max: 64)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:import, 'marty', 'mcfly', [:memory, 1, :min, 1, :max, 64]] }
+    end
+  end
+
+  describe 'When importing a table' do
+    before do
+      import.table(1, :funcref, min: 1, max: 64)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:import, 'marty', 'mcfly', [:table, 1, :funcref, :min, 1, :max, 64]] }
+    end
+  end
+
+  describe 'When importing a function' do
+    before do
+      import.func(:foo) do
+        param(:f32, :f64)
+        result(:i32)
+      end
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:import, 'marty', 'mcfly', [:func, :$foo, %i[param f32 f64], %i[result i32]]] }
+    end
+  end
+
+  describe 'When importing a global' do
+    before do
+      import.global(:foo, :i32)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:import, 'marty', 'mcfly', %i[global $foo i32]] }
+    end
+  end
+end
diff --git a/spec/wag/module_spec.rb b/spec/wag/module_spec.rb
new file mode 100644
index 0000000..d43b587
--- /dev/null
+++ b/spec/wag/module_spec.rb
@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe WAG::Module do
+  let(:mod) { described_class.new }
+  subject { mod }
+
+  describe 'When the module is empty' do
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module] }
+    end
+
+    describe '#to_wat' do
+      subject { super().to_wat }
+      it { is_expected.to eq '(module)' }
+    end
+  end
+
+  describe 'When the module imports a memory' do
+    before do
+      mod.import('js', 'memory').memory(1)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:import, 'js', 'memory', [:memory, 1]]] }
+    end
+  end
+
+  describe 'When the module exports a memory' do
+    before do
+      mod.export('memory').memory(1)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:export, 'memory', [:memory, 1]]] }
+    end
+  end
+
+  describe 'When the module declares a memory' do
+    before do
+      mod.memory(2)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:memory, 2]] }
+    end
+  end
+
+  describe 'When the module declares a global' do
+    before do
+      mod.global(:foo, :i32)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, %i[global $foo i32]] }
+    end
+  end
+
+  describe 'When the module declares a type' do
+    before do
+      mod.type(:foo) do
+        param(:i32)
+        result(:i32)
+      end
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:type, :$foo, [:func, %i[param i32], %i[result i32]]]] }
+    end
+  end
+
+  describe 'When the module declares a table element' do
+    before do
+      mod.elem(1, :foo1, :foo2)
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:elem, [:"i32.const", 1], :$foo1, :$foo2]] }
+    end
+  end
+
+  describe 'When the module declares data' do
+    before do
+      mod.data(16, 'Hello World')
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:data, [:"i32.const", 16], 'Hello World']] }
+    end
+  end
+
+  describe 'When the module declares a function' do
+    before do
+      mod.func(:add) do
+        param(:i32, :i32)
+        result(:i32)
+      end
+    end
+
+    describe '#to_sexpr' do
+      subject { super().to_sexpr }
+      it { is_expected.to eq [:module, [:func, :$add, %i[param i32 i32], %i[result i32]]] }
+    end
+  end
+end
diff --git a/spec/wag_spec.rb b/spec/wag_spec.rb
index 8b09cbb..6bdee36 100644
--- a/spec/wag_spec.rb
+++ b/spec/wag_spec.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-RSpec.describe Wag do
+RSpec.describe WAG do
   it 'has a version number' do
-    expect(Wag::VERSION).not_to be nil
+    expect(WAG::VERSION).not_to be nil
   end
 end
diff --git a/wag.gemspec b/wag.gemspec
index acdd75d..81bd926 100644
--- a/wag.gemspec
+++ b/wag.gemspec
@@ -4,7 +4,7 @@ require_relative 'lib/wag/version'
 
 Gem::Specification.new do |spec|
   spec.name          = 'wag'
-  spec.version       = Wag::VERSION
+  spec.version       = WAG::VERSION
   spec.authors       = ['James Harton']
   spec.email         = ['james@automat.nz']
 
@@ -30,4 +30,6 @@ Gem::Specification.new do |spec|
   spec.bindir        = 'exe'
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
+
+  spec.add_runtime_dependency('dry-inflector', '~> 0.2.0')
 end