diff --git a/README.md b/README.md
index 93507f9..ac01a5e 100644
--- a/README.md
+++ b/README.md
@@ -103,7 +103,7 @@ obj.key
 
 You can get png file directly from Texture2D asset. Output object's class is `ChunkyPNG::Image`.
 
-Acceptable format is basic texture formats (1, 2, 3, 4, 5, 7 and 13) and ETC_RGB4 (34).
+Only some basic texture formats (1--5, 7, 9, 13--20, 22, 62, and 63) and ETC_RGB4 (34) are available.
 
 ```ruby
 require 'mikunyan/decoders'
@@ -118,6 +118,8 @@ img = Mikunyan::ImageDecoder.decode_object(obj)
 img.save('mikunyan.png')
 ```
 
+Mikunyan cannot decode ASTC files. Use `Mikunyan::ImageDecoder.create_astc_file` instead.
+
 ### Json / YAML Outputer
 
 `mikunyan-json` is an executable command for converting unity3d to json.
diff --git a/lib/mikunyan.rb b/lib/mikunyan.rb
index dae3e45..86037a6 100644
--- a/lib/mikunyan.rb
+++ b/lib/mikunyan.rb
@@ -6,3 +6,7 @@ require "mikunyan/binary_reader"
 require "mikunyan/object_value"
 require "mikunyan/type_tree"
 require "mikunyan/constants"
+
+# Module for deserializing Unity Assets and AssetBundles
+module Mikunyan
+end
diff --git a/lib/mikunyan/asset.rb b/lib/mikunyan/asset.rb
index 039d272..dae625d 100644
--- a/lib/mikunyan/asset.rb
+++ b/lib/mikunyan/asset.rb
@@ -1,21 +1,133 @@
 module Mikunyan
+    # Class for representing Unity Asset
+    # @attr_reader [String] name Asset name
+    # @attr_reader [Integer] format file format number
+    # @attr_reader [String] generator_version version string of generator
+    # @attr_reader [Integer] target_platform target platform number
+    # @attr_reader [Symbol] endian data endianness (:little or :big)
+    # @attr_reader [Array<Mikunyan::Asset::Klass>] klasses defined classes
+    # @attr_reader [Array<Mikunyan::Asset::ObjectData>] objects included objects
+    # @attr_reader [Array<Integer>] add_ids ?
+    # @attr_reader [Array<Mikunyan::Asset::Reference>] references reference data
     class Asset
-        attr_accessor :name, :format, :generator_version, :target_platform, :endian, :klasses, :objects, :add_ids, :references
+        attr_reader :name, :format, :generator_version, :target_platform, :endian, :klasses, :objects, :add_ids, :references
+
+        # Struct for representing Asset class definition
+        # @attr [Integer] class_id class ID
+        # @attr [Integer,nil] script_id script ID
+        # @attr [String] hash hash value (16 or 32 bytes)
+        # @attr [Mikunyan::TypeTree, nil] type_tree given TypeTree
         Klass = Struct.new(:class_id, :script_id, :hash, :type_tree)
+
+        # Struct for representing Asset object information
+        # @attr [Integer] path_id path ID
+        # @attr [Integer] offset data offset
+        # @attr [Integer] size data size
+        # @attr [Integer,nil] type_id type ID
+        # @attr [Integer,nil] class_id class ID
+        # @attr [Integer,nil] class_idx class definition index
+        # @attr [Boolean] destroyed? destroyed or not
+        # @attr [String] data binary data of object
         ObjectData = Struct.new(:path_id, :offset, :size, :type_id, :class_id, :class_idx, :destroyed?, :data)
+
+        # Struct for representing Asset reference information
+        # @attr [String] path path
+        # @attr [String] guid GUID (16 bytes)
+        # @attr [Integer] type ?
+        # @attr [String] file_path Asset name
         Reference = Struct.new(:path, :guid, :type, :file_path)
 
+        # Load Asset from binary string
+        # @param [String] bin binary data
+        # @param [String] name Asset name
+        # @return [Mikunyan::Asset] deserialized Asset object
+        def self.load(bin, name)
+            r = Asset.new(name)
+            r.send(:load, bin)
+            r
+        end
+
+        # Load Asset from file
+        # @param [String] file file name
+        # @param [String] name Asset name (automatically generated if not specified)
+        # @return [Mikunyan::Asset] deserialized Asset object
+        def self.file(file, name=nil)
+            name = File.basename(name, '.*') unless name
+            Asset.load(File.binread(file), name)
+        end
+
+        # Returns list of all path IDs
+        # @return [Array<Integer>] list of all path IDs
+        def path_ids
+            @objects.map{|e| e.path_id}
+        end
+
+        # Returns list of containers
+        # @return [Array<Hash>,nil] list of all containers
+        def containers
+            obj = parse_object(1)
+            return nil unless obj && obj.m_Container && obj.m_Container.array?
+            obj.m_Container.value.map do |e|
+                {:name => e.first.value, :preload_index => e.second.preloadIndex.value, :path_id => e.second.asset.m_PathID.value}
+            end
+        end
+
+        # Parse object of given path ID
+        # @param [Integer,ObjectData] path_id path ID or object
+        # @return [Mikunyan::ObjectValue,nil] parsed object
+        def parse_object(path_id)
+            if path_id.class == Integer
+                obj = @objects.find{|e| e.path_id == path_id}
+                return nil unless obj
+            elsif path_id.class == ObjectData
+                obj = path_id
+            else
+                return nil
+            end
+
+            klass = (obj.class_idx ? @klasses[obj.class_idx] : @klasses.find{|e| e.class_id == obj.class_id} || @klasses.find{|e| e.class_id == obj.type_id})
+            type_tree = Asset.parse_type_tree(klass)
+            return nil unless type_tree
+
+            parse_object_private(BinaryReader.new(obj.data, @endian), type_tree)
+        end
+
+        # Parse object of given path ID and simplify it
+        # @param [Integer,ObjectData] path_id path ID or object
+        # @return [Hash,nil] parsed object
+        def parse_object_simple(path_id)
+            Asset.object_simplify(parse_object(path_id))
+        end
+
+        # Returns object type name string
+        # @param [Integer,ObjectData] path_id path ID or object
+        # @return [String,nil] type name
+        def object_type(path_id)
+            if path_id.class == Integer
+                obj = @objects.find{|e| e.path_id == path_id}
+                return nil unless obj
+            elsif path_id.class == ObjectData
+                obj = path_id
+            else
+                return nil
+            end
+            klass = (obj.class_idx ? @klasses[obj.class_idx] : @klasses.find{|e| e.class_id == obj.class_id} || @klasses.find{|e| e.class_id == obj.type_id})
+            if klass && klass.type_tree && klass.type_tree.nodes[0]
+                klass.type_tree.nodes[0].type
+            elsif klass
+                Mikunyan::CLASS_ID[klass.class_id]
+            else
+                nil
+            end
+        end
+
+        private
+
         def initialize(name)
             @name = name
             @endian = :big
         end
 
-        def self.file(file, name)
-            r = Asset.new(name)
-            r.load(File.binread(file))
-            r
-        end
-
         def load(bin)
             br = BinaryReader.new(bin)
             metadata_size = br.i32u
@@ -108,97 +220,6 @@ module Mikunyan
             end
         end
 
-        def path_ids
-            @objects.map{|e| e.path_id}
-        end
-
-        def containers
-            obj = parse_object(1)
-            return nil unless obj && obj.m_Container && obj.m_Container.array?
-            obj.m_Container.value.map do |e|
-                {:name => e.first.value, :preload_index => e.second.preloadIndex.value, :path_id => e.second.asset.m_PathID.value}
-            end
-        end
-
-        def parse_object(path_id)
-            if path_id.class == Integer
-                obj = @objects.find{|e| e.path_id == path_id}
-                return nil unless obj
-            elsif path_id.class == ObjectData
-                obj = path_id
-            else
-                return nil
-            end
-
-            klass = (obj.class_idx ? @klasses[obj.class_idx] : @klasses.find{|e| e.class_id == obj.class_id} || @klasses.find{|e| e.class_id == obj.type_id})
-            type_tree = Asset.parse_type_tree(klass)
-            return nil unless type_tree
-
-            parse_object_private(BinaryReader.new(obj.data, @endian), type_tree)
-        end
-
-        def parse_object_simple(path_id)
-            Asset.object_simplify(parse_object(path_id))
-        end
-
-        def object_type(path_id)
-            if path_id.class == Integer
-                obj = @objects.find{|e| e.path_id == path_id}
-                return nil unless obj
-            elsif path_id.class == ObjectData
-                obj = path_id
-            else
-                return nil
-            end
-            klass = (obj.class_idx ? @klasses[obj.class_idx] : @klasses.find{|e| e.class_id == obj.class_id} || @klasses.find{|e| e.class_id == obj.type_id})
-            if klass && klass.type_tree && klass.type_tree.nodes[0]
-                klass.type_tree.nodes[0].type
-            elsif klass
-                Mikunyan::CLASS_ID[klass.class_id]
-            else
-                nil
-            end
-        end
-
-        def self.parse_type_tree(klass)
-            return nil unless klass.type_tree
-            nodes = klass.type_tree.nodes
-            tree = {}
-            stack = []
-            nodes.each do |node|
-                this = {:name => node.name, :node => node, :children => []}
-                if node.depth == 0
-                    tree = this
-                else
-                    stack[node.depth - 1][:children] << this
-                end
-                stack[node.depth] = this
-            end
-            tree
-        end
-
-        def self.object_simplify(obj)
-            if obj.class != ObjectValue
-                obj
-            elsif obj.type == 'pair'
-                [object_simplify(obj['first']), object_simplify(obj['second'])]
-            elsif obj.type == 'map' && obj.array?
-                obj.value.map{|e| [object_simplify(e['first']), object_simplify(e['second'])] }.to_h
-            elsif obj.value?
-                object_simplify(obj.value)
-            elsif obj.array?
-                obj.value.map{|e| object_simplify(e)}
-            else
-                hash = {}
-                obj.keys.each do |key|
-                    hash[key] = object_simplify(obj[key])
-                end
-                hash
-            end
-        end
-
-        private
-
         def parse_object_private(br, type_tree)
             r = nil
             node = type_tree[:node]
@@ -267,5 +288,42 @@ module Mikunyan
             br.align(4) if node.flags & 0x4000 != 0
             r
         end
+
+        def self.object_simplify(obj)
+            if obj.class != ObjectValue
+                obj
+            elsif obj.type == 'pair'
+                [object_simplify(obj['first']), object_simplify(obj['second'])]
+            elsif obj.type == 'map' && obj.array?
+                obj.value.map{|e| [object_simplify(e['first']), object_simplify(e['second'])] }.to_h
+            elsif obj.value?
+                object_simplify(obj.value)
+            elsif obj.array?
+                obj.value.map{|e| object_simplify(e)}
+            else
+                hash = {}
+                obj.keys.each do |key|
+                    hash[key] = object_simplify(obj[key])
+                end
+                hash
+            end
+        end
+
+        def self.parse_type_tree(klass)
+            return nil unless klass.type_tree
+            nodes = klass.type_tree.nodes
+            tree = {}
+            stack = []
+            nodes.each do |node|
+                this = {:name => node.name, :node => node, :children => []}
+                if node.depth == 0
+                    tree = this
+                else
+                    stack[node.depth - 1][:children] << this
+                end
+                stack[node.depth] = this
+            end
+            tree
+        end
     end
 end
diff --git a/lib/mikunyan/asset_bundle.rb b/lib/mikunyan/asset_bundle.rb
index 1c65de4..97899ee 100644
--- a/lib/mikunyan/asset_bundle.rb
+++ b/lib/mikunyan/asset_bundle.rb
@@ -1,19 +1,33 @@
 require 'extlz4'
 
 module Mikunyan
+    # Class for representing Unity AssetBundle
+    # @attr_reader [String] signature file signature (UnityRaw or UnityFS)
+    # @attr_reader [Integer] format file format number
+    # @attr_reader [String] unity_version version string of Unity to use this AssetBundle
+    # @attr_reader [String] generator_version version string of generator
+    # @attr_reader [Array<Mikunyan::Asset>] assets included Assets
     class AssetBundle
-        attr_accessor :signature, :format, :unity_version, :generator_version, :assets
+        attr_reader :signature, :format, :unity_version, :generator_version, :assets
 
+        # Load AssetBundle from binary string
+        # @param [String] bin binary data
+        # @return [Mikunyan::AssetBundle] deserialized AssetBundle object
         def self.load(bin)
             r = AssetBundle.new
-            r.load(bin)
+            r.send(:load, bin)
             r
         end
 
+        # Load AssetBundle from file
+        # @param [String] file file name
+        # @return [Mikunyan::AssetBundle] deserialized AssetBundle object
         def self.file(file)
             AssetBundle.load(File.binread(file))
         end
 
+        private
+
         def load(bin)
             br = BinaryReader.new(bin)
             @signature = br.cstr
@@ -31,8 +45,6 @@ module Mikunyan
             end
         end
 
-        private
-
         def load_unity_raw(br)
             @assets = []
 
@@ -48,8 +60,7 @@ module Mikunyan
                 asset_size = br.i32u
                 br.jmp(asset_pos + asset_header_size - 4)
                 asset_data = br.read(asset_size)
-                asset = Asset.new(asset_name)
-                asset.load(asset_data)
+                asset = Asset.load(asset_data, asset_name)
                 @assets << asset
             end
         end
@@ -77,8 +88,7 @@ module Mikunyan
             blocks.each{|b| raw_data << uncompress(br.read(b[:c]), b[:u], b[:f])}
 
             asset_blocks.each do |b|
-                asset = Asset.new(b[:name])
-                asset.load(raw_data.byteslice(b[:offset], b[:size]))
+                asset = Asset.load(raw_data.byteslice(b[:offset], b[:size]), b[:name])
                 @assets << asset
             end
         end
diff --git a/lib/mikunyan/binary_reader.rb b/lib/mikunyan/binary_reader.rb
index d5758c4..1e8beeb 100644
--- a/lib/mikunyan/binary_reader.rb
+++ b/lib/mikunyan/binary_reader.rb
@@ -1,9 +1,16 @@
 require 'bin_utils'
 
 module Mikunyan
+    # Class for manipulating binary string
+    # @attr [Symbol] endian endianness
+    # @attr [Integer] pos position
+    # @attr [Integer] length data size
     class BinaryReader
         attr_accessor :endian, :pos, :length
 
+        # Constructor
+        # @param [String] data binary string
+        # @param [Symbol] endian endianness
         def initialize(data, endian = :big)
             @data = data
             @pos = 0
@@ -11,104 +18,131 @@ module Mikunyan
             @endian = endian
         end
 
+        # Returns whether little endian or not
+        # @return [Boolean]
         def little?
             @endian == :little
         end
 
-        def jmp(pos = 0)
+        # Jump to given position
+        # @param [Integer] pos position
+        def jmp(pos=0)
             @pos = pos
         end
 
-        def adv(size = 0)
+        # Advance position given size
+        # @param [Integer] size size
+        def adv(size=0)
             @pos += size
         end
 
+        # Round up position to multiple of given size
+        # @param [Integer] size size
         def align(size)
             @pos = (@pos + size - 1) / size * size
         end
 
+        # Read given size of binary string and seek
+        # @param [Integer] size size
+        # @return [String] data
         def read(size)
             data = @data.byteslice(@pos, size)
             @pos += size
             data
         end
 
+        # Read string until null character
+        # @return [String] string
         def cstr
             r = @data.unpack("@#{pos}Z*")[0]
             @pos += r.bytesize + 1
             r
         end
 
+        # Read 8bit signed integer
         def i8
             i8s
         end
 
+        # Read 8bit signed integer
         def i8s
             r = BinUtils.get_sint8(@data, @pos)
             @pos += 1
             r
         end
 
+        # Read 8bit unsigned integer
         def i8u
             r = BinUtils.get_int8(@data, @pos)
             @pos += 1
             r
         end
 
+        # Read 16bit signed integer
         def i16
             i16s
         end
 
+        # Read 16bit signed integer
         def i16s
             r = little? ? BinUtils.get_sint16_le(@data, @pos) : BinUtils.get_sint16_be(@data, @pos)
             @pos += 2
             r
         end
 
+        # Read 16bit unsigned integer
         def i16u
             r = little? ? BinUtils.get_int16_le(@data, @pos) : BinUtils.get_int16_be(@data, @pos)
             @pos += 2
             r
         end
 
+        # Read 32bit signed integer
         def i32
             i32s
         end
 
+        # Read 32bit signed integer
         def i32s
             r = little? ? BinUtils.get_sint32_le(@data, @pos) : BinUtils.get_sint32_be(@data, @pos)
             @pos += 4
             r
         end
 
+        # Read 32bit unsigned integer
         def i32u
             r = little? ? BinUtils.get_int32_le(@data, @pos) : BinUtils.get_int32_be(@data, @pos)
             @pos += 4
             r
         end
 
+        # Read 64bit signed integer
         def i64
             i64s
         end
 
+        # Read 64bit signed integer
         def i64s
             r = little? ? BinUtils.get_sint64_le(@data, @pos) : BinUtils.get_sint64_be(@data, @pos)
             @pos += 8
             r
         end
 
+        # Read 64bit unsigned integer
         def i64u
             r = little? ? BinUtils.get_int64_le(@data, @pos) : BinUtils.get_int64_be(@data, @pos)
             @pos += 8
             r
         end
 
+        # Read 32bit floating point value
         def float
             r = little? ? @data.byteslice(@pos, 4).unpack('e')[0] : @data.byteslice(@pos, 4).unpack('g')[0]
             @pos += 4
             r
         end
 
+        # Read 64bit floating point value
         def double
             r = little? ? @data.byteslice(@pos, 8).unpack('E')[0] : @data.byteslice(@pos, 8).unpack('G')[0]
             @pos += 8
diff --git a/lib/mikunyan/constants.rb b/lib/mikunyan/constants.rb
index d15e0a4..4142c13 100644
--- a/lib/mikunyan/constants.rb
+++ b/lib/mikunyan/constants.rb
@@ -1,4 +1,5 @@
 module Mikunyan
+    private
     STRING_TABLE = {
         0=>'AABB',
         5=>'AnimationClip',
diff --git a/lib/mikunyan/decoders/image_decoder.rb b/lib/mikunyan/decoders/image_decoder.rb
index 48214c3..e3930bf 100644
--- a/lib/mikunyan/decoders/image_decoder.rb
+++ b/lib/mikunyan/decoders/image_decoder.rb
@@ -3,10 +3,11 @@ require 'bin_utils'
 require 'fiddle'
 
 module Mikunyan
+    # Class for image decoding tools
     class ImageDecoder
-        Etc1ModifierTable = [[2, 8], [5, 17], [9, 29], [13, 42], [18, 60], [24, 80], [33, 106], [47, 183]]
-        Etc1SubblockTable = [[0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1], [0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1]]
-
+        # Decode image from Mikunyan::ObjectValue
+        # @param [Mikunyan::ObjectValue] object object to decode
+        # @return [ChunkyPNG::Image,nil] decoded image
         def self.decode_object(object)
             return nil unless object.class == ObjectValue
 
@@ -66,8 +67,12 @@ module Mikunyan
             end
         end
 
-        # 4 bit integer per color
-
+        # Decode image from RGBA4444 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgba4444(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 4)
             (width * height).times do |i|
@@ -78,6 +83,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
+        # Decode image from ARGB4444 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_argb4444(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 4)
             (width * height).times do |i|
@@ -88,8 +99,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
-        # 5-6 bit integer per color
-
+        # Decode image from RGB565 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgb565(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -102,8 +117,11 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
-        # 8 bit integer per color
-
+        # Decode image from A8 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_a8(width, height, bin)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -113,10 +131,20 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from R8 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_r8(width, height, bin)
             decode_a8(width, height, bin)
         end
 
+        # Decode image from RG16 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rg16(width, height, bin)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -125,14 +153,29 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from RGB24 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgb24(width, height, bin)
             ChunkyPNG::Image.from_rgb_stream(width, height, bin)
         end
 
+        # Decode image from RGBA32 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgba32(width, height, bin)
             ChunkyPNG::Image.from_rgba_stream(width, height, bin)
         end
 
+        # Decode image from ARGB32 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_argb32(width, height, bin)
             mem = String.new(capacity: width * height * 4)
             (width * height).times do |i|
@@ -142,6 +185,11 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
+        # Decode image from BGRA32 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_bgra32(width, height, bin)
             mem = String.new(capacity: width * height * 4)
             (width * height).times do |i|
@@ -151,8 +199,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
-        # 16 bit integer per color
-
+        # Decode image from R16 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_r16(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -163,8 +215,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
-        # 9 bit float per color
-
+        # Decode image from RGB9e5 binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgb9e5float(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -181,8 +237,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
-        # 16 bit (half) float per color
-
+        # Decode image from R Half-float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rhalf(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -192,6 +252,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from RG Half-float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rghalf(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             (width * height).times do |i|
@@ -202,6 +268,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from RGBA Half-float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgbahalf(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 4)
             (width * height).times do |i|
@@ -214,8 +286,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
-        # 32 bit float per color
-
+        # Decode image from R float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rfloat(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             unpackstr = endian == :little ? 'e' : 'g'
@@ -226,6 +302,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from RG float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgfloat(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 3)
             unpackstr = endian == :little ? 'e2' : 'g2'
@@ -236,6 +318,12 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(width, height, mem)
         end
 
+        # Decode image from RGBA float binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @param [Symbol] endian endianness of binary
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgbafloat(width, height, bin, endian = :big)
             mem = String.new(capacity: width * height * 4)
             unpackstr = endian == :little ? 'e4' : 'g4'
@@ -246,8 +334,11 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem)
         end
 
-        # other formats
-
+        # Decode image from ETC1 compressed binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_etc1(width, height, bin)
             bw = (width + 3) / 4
             bh = (height + 3) / 4
@@ -263,6 +354,9 @@ module Mikunyan
             ChunkyPNG::Image.from_rgb_stream(bw * 4, bh * 4, mem.to_str).crop!(0, 0, width, height)
         end
 
+        # Create ASTC file data from ObjectValue
+        # @param [Mikunyan::ObjectValue,Hash] object target object
+        # @return [String,nil] created file
         def self.create_astc_file(object)
             astc_list = {
                 48 => 4, 49 => 5, 50 => 6, 51 => 8, 52 => 10, 53 => 12,
@@ -290,6 +384,9 @@ module Mikunyan
 
         private
 
+        Etc1ModifierTable = [[2, 8], [5, 17], [9, 29], [13, 42], [18, 60], [24, 80], [33, 106], [47, 183]]
+        Etc1SubblockTable = [[0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1], [0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1]]
+
         def self.decode_etc1_block(bin)
             colors = []
             codes = [bin >> 37 & 7, bin >> 34 & 7]
diff --git a/lib/mikunyan/object_value.rb b/lib/mikunyan/object_value.rb
index 3d21591..a65ae55 100644
--- a/lib/mikunyan/object_value.rb
+++ b/lib/mikunyan/object_value.rb
@@ -1,7 +1,18 @@
 module Mikunyan
+    # Class for representing decoded object
+    # @attr [String] name object name
+    # @attr [String] type object type name
+    # @attr [Object] value object
+    # @attr [Symbol] endian endianness
+    # @attr [Boolean] is_struct
     class ObjectValue
         attr_accessor :name, :type, :value, :endian, :is_struct
 
+        # Constructor
+        # @param [String] name object name
+        # @param [String] type object type name
+        # @param [Symbol] endian endianness
+        # @param [Object] value object
         def initialize(name, type, endian, value = nil)
             @name = name
             @type = type
@@ -11,46 +22,70 @@ module Mikunyan
             @attr = {}
         end
 
+        # Return whether object is array or not
+        # @return [Boolean]
         def array?
             value && value.class == Array
         end
 
+        # Return whether object is value or not
+        # @return [Boolean]
         def value?
             value && value.class != Array
         end
 
+        # Return whether object is struct or not
+        # @return [Boolean]
         def struct?
             is_struct
         end
 
+        # Return all keys
+        # @return [Array] list of keys
         def keys
             @attr.keys
         end
 
+        # Return whether object contains key
+        # @param [String] key
+        # @return [Boolean]
         def key?(key)
             @attr.key?(key)
         end
 
+        # Return value
+        # @return [Object] value
         def []
             @value
         end
 
-        def [](name)
-            if array? && name.class == Integer
-                @value[name]
+        # Return value of selected index or key
+        # @param [Integer,String] i index or key
+        # @return [Object] value
+        def [](i)
+            if array? && i.class == Integer
+                @value[i]
             else
-                @attr[name]
+                @attr[i]
             end
         end
 
+        # Set value of selected key
+        # @param [String] name key
+        # @param [Object] value value
+        # @return [Object] value
         def []=(name, value)
             @attr[name] = value
         end
 
+        # Return value of called key
+        # @param [String] name key
+        # @return [Object] value
         def method_missing(name, *args)
             @attr[name.to_s]
         end
 
+        # Implementation of respond_to_missing?
         def respond_to_missing?(symbol, include_private)
             @attr.key?(symbol.to_s)
         end
diff --git a/lib/mikunyan/type_tree.rb b/lib/mikunyan/type_tree.rb
index 18abb53..4ea2d01 100644
--- a/lib/mikunyan/type_tree.rb
+++ b/lib/mikunyan/type_tree.rb
@@ -1,8 +1,22 @@
 module Mikunyan
+    # Class for representing TypeTree
+    # @attr [Array<Mikunyan::TypeTree::Node>] nodes list of all nodes
     class TypeTree
         attr_accessor :nodes
+
+        # Struct for representing Node in TypeTree
+        # @attr [String] version version string
+        # @attr [Integer] depth depth of node (>= 0)
+        # @attr [Boolean] array? array node or not
+        # @attr [String] type type name
+        # @attr [String] name node (attribute) name
+        # @attr [Integer] index index in node list
+        # @attr [Integer] flags flags of node
         Node = Struct.new(:version, :depth, :array?, :type, :name, :size, :index, :flags)
 
+        # Create TypeTree from binary string (new version)
+        # @param [Mikunyan::BinaryReader] br
+        # @return [Mikunyan::TypeTree] created TypeTree
         def self.load(br)
             nodes = []
             node_count = br.i32u
@@ -28,6 +42,9 @@ module Mikunyan
             r
         end
 
+        # Create TypeTree from binary string (legacy version)
+        # @param [Mikunyan::BinaryReader] br
+        # @return [Mikunyan::TypeTree] created TypeTree
         def self.load_legacy(br)
             nodes = []
             stack = [0]
@@ -49,6 +66,9 @@ module Mikunyan
             r
         end
 
+        # Create default TypeTree from hash string (if exists)
+        # @param [String] hash
+        # @return [Mikunyan::TypeTree,nil] created TypeTree
         def self.load_default(hash)
             hash_str = hash.unpack('H*')[0]
             file = File.expand_path("../typetrees/#{hash_str}.dat", __FILE__)
diff --git a/lib/mikunyan/version.rb b/lib/mikunyan/version.rb
index 49eba6b..af98074 100644
--- a/lib/mikunyan/version.rb
+++ b/lib/mikunyan/version.rb
@@ -1,3 +1,4 @@
 module Mikunyan
-  VERSION = "3.9.0"
+    # version string
+    VERSION = "3.9.0"
 end