diff --git a/include/core/area.h b/include/core/area.h
index dfa4d48..2a79a90 100644
--- a/include/core/area.h
+++ b/include/core/area.h
@@ -8,6 +8,15 @@
 namespace kku
 {
 
+/// Area
+///
+/// Consists of 2 arithmetic
+/// points that represent
+/// a rectangle position
+/// and 2 arithmetic
+/// lengths by x and y
+/// that represent
+/// rectangle coverage area
 template <typename T, typename = std::enable_if_t<std::is_arithmetic_v<T>>>
 struct Area
 {
diff --git a/include/core/bpmsection.h b/include/core/bpmsection.h
index ec2c18b..282dddb 100644
--- a/include/core/bpmsection.h
+++ b/include/core/bpmsection.h
@@ -5,14 +5,33 @@
 namespace kku
 {
 
+/// BPMSection
+///
+/// Data to setup and distinguish
+/// a section on beatmap timeline
 struct BPMSection
 {
+    /// Amount of beats
+    /// per minute in the section
     unsigned int bpm = 120; // Hi, osu
+
+    /// Denominator in fraction of major
+    /// beats. Like, 1/2, 1/3. etc...
     unsigned int fraction = 2;
+
+    /// Timestamp respresenting when
+    /// the section becomes active
     microsec offset_start = 0;
+
+    /// Interval between beats
     microsec interval = 0;
 };
 
+/// BPMSectionComparator
+///
+/// Predicate to define
+/// BPMSection sorting rule:
+/// by timestamp of start
 struct BPMSectionComparator
 {
     bool operator()(const BPMSection& lhs, const BPMSection& rhs) const noexcept
@@ -21,4 +40,4 @@ struct BPMSectionComparator
     }
 };
 
-}
\ No newline at end of file
+}
diff --git a/include/core/color.h b/include/core/color.h
index f0c599d..e17b970 100644
--- a/include/core/color.h
+++ b/include/core/color.h
@@ -3,6 +3,9 @@
 namespace kku
 {
 
+/// Color
+///
+/// Object of color data in RGBa
 struct Color
 {
     unsigned char red = 0;
@@ -11,4 +14,4 @@ struct Color
     unsigned char alpha = 0;
 };
 
-}
\ No newline at end of file
+}
diff --git a/include/core/corefactory.h b/include/core/corefactory.h
index 8c73f9e..5b899d8 100644
--- a/include/core/corefactory.h
+++ b/include/core/corefactory.h
@@ -13,6 +13,10 @@
 namespace kku
 {
 
+/// CoreFactory
+///
+/// Provides basic
+/// multimedia elements and data
 class CoreFactory
 {
 public:
diff --git a/include/core/editor.h b/include/core/editor.h
index a82c3b1..329774d 100644
--- a/include/core/editor.h
+++ b/include/core/editor.h
@@ -10,6 +10,10 @@
 namespace kku
 {
 
+/// Editor
+///
+/// Functional aggregation of
+/// logic for Editor game mode
 class Editor
 {
 public:
@@ -85,4 +89,4 @@ protected:
     std::set<BPMSection, BPMSectionComparator> _bpm_sections;
 };
 
-}
\ No newline at end of file
+}
diff --git a/include/core/game.h b/include/core/game.h
index 54e1a39..217ba94 100644
--- a/include/core/game.h
+++ b/include/core/game.h
@@ -6,6 +6,10 @@
 namespace kku
 {
 
+/// Game
+///
+/// Functional aggregation of
+/// logic for actual game mode
 class Game
 {
 public:
@@ -17,4 +21,4 @@ public:
     virtual void display() const = 0;
 };
 
-}
\ No newline at end of file
+}
diff --git a/include/core/line.h b/include/core/line.h
index 22d2d95..9170d65 100644
--- a/include/core/line.h
+++ b/include/core/line.h
@@ -6,6 +6,9 @@
 namespace kku
 {
 
+/// Line
+///
+/// Graphical 2D line
 class Line
 {
 public:
@@ -15,4 +18,4 @@ public:
     virtual void display() = 0;
 };
 
-}
\ No newline at end of file
+}
diff --git a/include/core/music.h b/include/core/music.h
index a1aa949..d968616 100644
--- a/include/core/music.h
+++ b/include/core/music.h
@@ -7,6 +7,9 @@
 namespace kku
 {
 
+/// Music
+///
+/// Object for streaming music file
 class Music
 {
 public:
diff --git a/include/core/vector.h b/include/core/vector.h
index 7a8fd02..871201d 100644
--- a/include/core/vector.h
+++ b/include/core/vector.h
@@ -5,11 +5,10 @@
 namespace kku
 {
 
-/* Meaning an element of a vector space in math.
- * Don't mistake for std::vector<T>
- * For now we don't need it as a special class,
- * so let it be a wrapper.                      */
-
+/// Vector2
+///
+/// Meaning an element of a vector space in math.
+/// Don't mistake for std::vector<T>
 template <typename T>
 using Vector2 = std::pair<T, T>;