diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0dbeea3..cf677b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 - Fix version links in CHANGELOG.md
 - Fix refresh icon font
+- Add code comments
+- Return always boolean in `setLocalStorageItem()`
 
 ## [0.1.4][] - 2022-05-04
 
diff --git a/public/css/notes.css b/public/css/notes.css
index edb1167..65e3d96 100644
--- a/public/css/notes.css
+++ b/public/css/notes.css
@@ -47,7 +47,8 @@
 .note[data-content='c4']::after,
 .note[data-content='h3']::after,
 .note[data-content='e2']::after,
-.note[data-content='d2']::after {
+.note[data-content='d2']::after,
+.note[data-content='a5']::after {
   content: '';
   position: absolute;
   background: #0f172a;
@@ -57,6 +58,7 @@
 }
 
 .note[data-content='c4']::after,
-.note[data-content='e2']::after {
+.note[data-content='e2']::after,
+.note[data-content='a5']::after {
   top: 50%;
 }
diff --git a/public/game.html b/public/game.html
index 12d75c4..88d3b77 100644
--- a/public/game.html
+++ b/public/game.html
@@ -105,6 +105,7 @@
     <script src="https://cdn.jsdelivr.net/npm/vexflow/build/cjs/vexflow.js"></script>
     <script src="js/general.js"></script>
     <script src="js/storage.js"></script>
+    <script src="js/generation.js"></script>
     <script src="js/notes.js"></script>
     <script src="js/game.js"></script>
   </body>
diff --git a/public/js/general.js b/public/js/general.js
index a4eb889..2fc6e0d 100644
--- a/public/js/general.js
+++ b/public/js/general.js
@@ -1,9 +1,36 @@
 'use strict';
 
+/**
+ * Alias for document.getElementById
+ * @param {!string} id - Element's id
+ * @returns {Element}
+ */
 const getElement = (id) => document.getElementById(id);
 
+/**
+ * Alias for document.createElement
+ * @param {string} [tag=div] - HTML tag
+ * @returns {Element}
+ */
 const createElement = (tag = 'div') => document.createElement(tag);
 
+/**
+ * An object that describes the basic properties
+ * of an HTML element to be created
+ * @typedef {Object} CustomElement
+ * @property {!string} tag - HTML-tag
+ * @property {!string} name - Element's identification string
+ * @property {string[]} [classes] - List of classes to add
+ * @property {Object.<string, string>[]} [attributes] - List of atttributes to add
+ * @property {string} [parent] - The parent of the object to which the item will be added.
+ *    name of the element, which is in the array before
+ */
+
+/**
+ * Quick creation of HTML elements
+ * @param {CustomElement[]} data - Elements to create
+ * @returns {Object.<string, Element>}
+ */
 const createElements = (data) => {
   const resultElements = {};
   for (const { tag, classes, attributes, name, parent } of data) {
@@ -19,12 +46,25 @@ const createElements = (data) => {
   return resultElements;
 };
 
+/**
+ * Finds data by the path (eg. "path.to.string")
+ * @param {Object} object - Object, to search in
+ * @param {string} path - Path (eg. "path.to.string")
+ * @returns {any} - Data that are by the path stored
+ */
 const resolvePath = (object, path) => {
   const steps = path.split('.');
   for (const step of steps) object = object[step];
   return object;
 };
 
+/**
+ * Updates value in object by the path (eg. "path.to.string")
+ * @param {Object} object - Object, to search in
+ * @param {string} path - Path (eg. "path.to.string")
+ * @param {any} value - New value
+ * @returns {undefined}
+ */
 const updateValueByPath = (object, path, value) =>
   path.split('.').reduce((o, p, i) => (o[p] = path.split('.').length === ++i ? value : o[p] || {}), object);
 
diff --git a/public/js/notes.js b/public/js/notes.js
index d70d4e8..906f3f0 100644
--- a/public/js/notes.js
+++ b/public/js/notes.js
@@ -2,31 +2,59 @@
 
 const NOTES_PX_OFFSET = 10;
 const mainNotes = { g: ['e', 5], f: ['g', 3] };
-
 const naturalNotes = ['c', 'd', 'e', 'f', 'g', 'a', 'h'];
 
+/**
+ * @typedef {('f'|'g')} Clef
+ */
+
+/**
+ * Get margin for note (px)
+ * @param {string!} note - Note (eg. C#4, Eb5, A2)
+ * @param {Clef} clef - Clef
+ * @returns {number} - Amount of px for element to be omit
+ */
 const getMargin = (note, clef) => {
+  // Parse given note. Get natural and ocatve
   const [naturalNote, octave] = [note[0].toLowerCase(), +note[note.length - 1]];
   const naturalNoteIndex = naturalNotes.findIndex((n) => n === naturalNote);
+  // The main note is the one between the first and second line (top: 0px)
+  // Parse its natural value and octave
   const [mainNote, mainOctave] = mainNotes[clef];
   const mainNoteIndex = naturalNotes.findIndex((n) => n === mainNote);
+  // If the note is in the same octave as the main note,
+  // return the index difference
   if (mainOctave === octave) {
     const result = (mainNoteIndex - naturalNoteIndex) * NOTES_PX_OFFSET;
+    // If the note equals the main note and the result is 0, then return 1.
+    // This is because the distance between the lines is 19px
+    // and there is a 1px hole, when we use top: 0px;
     return result === 0 ? 1 : result;
   }
+  // Count the number of notes that are between the note and the main one
   const octaveAmount = Math.abs(mainOctave - octave);
   const notesAmount = octaveAmount * naturalNotes.length;
   return (notesAmount - naturalNoteIndex + mainNoteIndex) * NOTES_PX_OFFSET;
 };
 
+/**
+ * Creates an element with stave, specified clef and notes
+ * @param {string!} containerId - Id of an element, to append stave in
+ * @param {Object} task - Task object
+ * @param {Clef} task.clef - Clef
+ * @param {string[]} task.notes - Notes
+ */
 const createStave = (containerId, { clef, notes }) => {
+  // Check the container
   const container = window.getElement(containerId);
   if (!container) throw new Error('Element not found');
+  // Create array of custom elements for quick creation
   const elementsToCreate = [
     { name: 'stave', classes: ['stave'] },
     { name: 'clefElement', classes: ['clef', clef], parent: 'stave' },
     { name: 'notesContainer', classes: ['notes'], parent: 'stave' },
   ];
+  // Add every note to stave
   for (const [i, note] of Object.entries(notes)) {
     const margin = getMargin(note, clef);
     elementsToCreate.push({
@@ -36,6 +64,7 @@ const createStave = (containerId, { clef, notes }) => {
       parent: 'notesContainer',
     });
   }
+  // Append stave into container
   const { stave } = window.createElements(elementsToCreate);
   container.appendChild(stave);
 };
diff --git a/public/js/storage.js b/public/js/storage.js
index 0e6e013..34494cb 100644
--- a/public/js/storage.js
+++ b/public/js/storage.js
@@ -1,5 +1,12 @@
 'use strict';
 
+/**
+ * Gets JSON from local storage and parses it
+ * @param {string!} key - Key
+ * @param {boolean} [deleteOnError=true] - Whether to delete the current value of an element
+ *    if an error occurred while parsing it
+ * @returns {Object}
+ */
 const getLocalStorageItem = (key, deleteOnError = true) => {
   try {
     const raw = window.localStorage.getItem(key);
@@ -12,6 +19,13 @@ const getLocalStorageItem = (key, deleteOnError = true) => {
   }
 };
 
+/**
+ * Set the new value of the item in local storage.
+ * The data passes the stringify
+ * @param {string!} key - Key
+ * @param {Object} data - JSON data to store
+ * @returns {boolean} - Whether or not it's successful
+ */
 const setLocalStorageItem = (key, data) => {
   try {
     const stringifiedData = JSON.stringify(data);
@@ -19,11 +33,20 @@ const setLocalStorageItem = (key, data) => {
     return true;
   } catch (err) {
     console.error(err);
-    return null;
+    return false;
   }
 };
 
+/**
+ * Alias for getLocalStorageItem('settings')
+ * @returns {Settings}
+ */
 const getSettings = () => getLocalStorageItem('settings');
+/**
+ * Alias for setLocalStorageItem('settings', newData);
+ * @param {Settings} [newData=window.gameSettings] - New settings object
+ * @returns {boolean} - Whether or not it's successful
+ */
 const updateSettings = (newData = window.gameSettings) => setLocalStorageItem('settings', newData);
 
 const getState = () => getLocalStorageItem('state');