diff --git a/.yarn/install-state.gz b/.yarn/install-state.gz
index 4abda704..706c9a99 100644
Binary files a/.yarn/install-state.gz and b/.yarn/install-state.gz differ
diff --git a/public/assets/demo.css b/public/assets/demo.css
index f1141266..35bfab62 100644
--- a/public/assets/demo.css
+++ b/public/assets/demo.css
@@ -3,417 +3,415 @@
  */
 
 :root {
-  --color-bg-main: #fff;
-  --color-border-light: #E8E8EB;
-  --color-text-main: #000;
+    --color-bg-main: #fff;
+    --color-border-light: #e8e8eb;
+    --color-text-main: #000;
 }
 
 .dark-mode {
-  --color-border-light: rgba(255, 255, 255,.08);
-  --color-bg-main: #1c1e24;
-  --color-text-main: #737886;
+    --color-border-light: rgba(255, 255, 255, 0.08);
+    --color-bg-main: #1c1e24;
+    --color-text-main: #737886;
 }
 
-
 body {
-  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
-  font-size: 14px;
-  line-height: 1.5em;
-  margin: 0;
-  background: var(--color-bg-main);
-  color: var(--color-text-main);
+    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
+    font-size: 14px;
+    line-height: 1.5em;
+    margin: 0;
+    background: var(--color-bg-main);
+    color: var(--color-text-main);
 }
 
 .ce-example {
-  font-size: 16.2px;
+    font-size: 16.2px;
 }
 
 .ce-example__header {
-  border-bottom: 1px solid var(--color-border-light);
-  height: 50px;
-  line-height: 50px;
-  display: flex;
-  padding: 0 30px;
-  margin-bottom: 30px;
-  flex-wrap: wrap;
+    border-bottom: 1px solid var(--color-border-light);
+    height: 50px;
+    line-height: 50px;
+    display: flex;
+    padding: 0 30px;
+    margin-bottom: 30px;
+    flex-wrap: wrap;
 }
 
 .ce-example__header a {
-  color: inherit;
-  text-decoration: none;
+    color: inherit;
+    text-decoration: none;
 }
 
 .ce-example__header-logo {
-  font-weight: bold;
+    font-weight: bold;
 }
 
 .ce-example__header-menu {
-  margin-left: auto;
+    margin-left: auto;
 }
 
-@media all and (max-width: 730px){
-  .ce-example__header-menu {
-    margin-left: 0;
-    margin-top: 10px;
-    flex-basis: 100%;
-    font-size: 14px;
-  }
+@media all and (max-width: 730px) {
+    .ce-example__header-menu {
+        margin-left: 0;
+        margin-top: 10px;
+        flex-basis: 100%;
+        font-size: 14px;
+    }
 }
 
 .ce-example__header-menu a {
-  margin-left: 20px;
+    margin-left: 20px;
 }
 
-@media all and (max-width: 730px){
-  .ce-example__header-menu a {
-    margin-left: 0;
-    margin-right: 15px;
-  }
+@media all and (max-width: 730px) {
+    .ce-example__header-menu a {
+        margin-left: 0;
+        margin-right: 15px;
+    }
 }
 
 .ce-example__content {
-  max-width: 1100px;
-  margin: 0 auto;
-  -webkit-font-smoothing: antialiased;
-  -moz-osx-font-smoothing: grayscale;
+    max-width: 1100px;
+    margin: 0 auto;
+    -webkit-font-smoothing: antialiased;
+    -moz-osx-font-smoothing: grayscale;
 }
 
 .thin-mode .ce-example__content {
-  max-width: 500px;
-  border-left: 1px solid #eee;
-  border-right: 1px solid #eee;
-  padding: 0 15px;
+    max-width: 500px;
+    border-left: 1px solid #eee;
+    border-right: 1px solid #eee;
+    padding: 0 15px;
 }
 
 .ce-example__output {
-  background: #1B202B;
-  overflow-x: auto;
-  padding: 0 30px 80px;
+    background: #1b202b;
+    overflow-x: auto;
+    padding: 0 30px 80px;
 }
 
 .ce-example__output-content {
-  max-width: 650px;
-  margin: 30px auto;
-  color: #ABADC3;
-  font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
-  font-size: 13.3px;
+    max-width: 650px;
+    margin: 30px auto;
+    color: #abadc3;
+    font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
+    font-size: 13.3px;
 }
 
 .ce-example__output-content:empty {
-  display: none;
+    display: none;
 }
 
 .ce-example__button {
-  display: block;
-  margin: 50px auto;
-  max-width: 180px;
-  background: #4A9DF8;
-  padding: 17px 30px;
-  box-shadow: 0 22px 18px -4px rgba(137, 207, 255, 0.77);
-  transition: all 150ms ease;
-  cursor: pointer;
-  border-radius: 31px;
-  color: #fff;
-  font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
-  text-align: center;
+    display: block;
+    margin: 50px auto;
+    max-width: 180px;
+    background: #4a9df8;
+    padding: 17px 30px;
+    box-shadow: 0 22px 18px -4px rgba(137, 207, 255, 0.77);
+    transition: all 150ms ease;
+    cursor: pointer;
+    border-radius: 31px;
+    color: #fff;
+    font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
+    text-align: center;
 }
 
 .ce-example__button:hover {
-  background: #3D8DE5;
-  transform: translateY(2px);
-  box-shadow: 0 20px 15px -4px rgba(137, 207, 255, 0.77);
+    background: #3d8de5;
+    transform: translateY(2px);
+    box-shadow: 0 20px 15px -4px rgba(137, 207, 255, 0.77);
 }
 
 .ce-example__output-footer {
-  padding: 30px 0;
-  font-size: 14.2px;
-  letter-spacing: 0.3px;
-  text-align: center;
+    padding: 30px 0;
+    font-size: 14.2px;
+    letter-spacing: 0.3px;
+    text-align: center;
 }
 
 .ce-example__output-footer a {
-  color: #fff;
-  text-decoration: none;
+    color: #fff;
+    text-decoration: none;
 }
 
 .ce-example__statusbar {
-  display: flex;
-  align-items: center;
-  position: fixed;
-  bottom: 0;
-  right: 0;
-  left: 0;
-  background: var(--color-bg-main);
-  border-radius: 8px 8px 0 0;
-  border-top: 1px solid var(--color-border-light);
-  box-shadow: 0 2px 6px var(--color-border-light);
-  font-size: 13px;
-  padding: 8px 15px;
-  z-index: 1;
-  user-select: none;
+    display: flex;
+    align-items: center;
+    position: fixed;
+    bottom: 0;
+    right: 0;
+    left: 0;
+    background: var(--color-bg-main);
+    border-radius: 8px 8px 0 0;
+    border-top: 1px solid var(--color-border-light);
+    box-shadow: 0 2px 6px var(--color-border-light);
+    font-size: 13px;
+    padding: 8px 15px;
+    z-index: 1;
+    user-select: none;
 }
 
 @media (max-width: 768px) {
-  .ce-example__statusbar {
-    display: none;
-  }
+    .ce-example__statusbar {
+        display: none;
+    }
 }
 
 .ce-example__statusbar-item:not(:last-of-type)::after {
-  content: '|';
-  color: #ddd;
-  margin: 0 15px 0 12px;
+    content: '|';
+    color: #ddd;
+    margin: 0 15px 0 12px;
 }
 
 .ce-example__statusbar-item--right {
-  margin-left: auto;
+    margin-left: auto;
 }
 
 .ce-example__statusbar-button {
-  display: inline-block;
-  padding: 3px 12px;
-  transition: all 150ms ease;
-  cursor: pointer;
-  border-radius: 31px;
-  background: #eff1f4;
-  text-align: center;
-  user-select: none;
+    display: inline-block;
+    padding: 3px 12px;
+    transition: all 150ms ease;
+    cursor: pointer;
+    border-radius: 31px;
+    background: #eff1f4;
+    text-align: center;
+    user-select: none;
 }
 
 .ce-example__statusbar-button:hover {
-  background: #e0e4eb;
+    background: #e0e4eb;
 }
 
 .ce-example__statusbar-button-primary {
-  background: #4A9DF8;
-  color: #fff;
-  box-shadow: 0 7px 8px -4px rgba(137, 207, 255, 0.77);
-  font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
+    background: #4a9df8;
+    color: #fff;
+    box-shadow: 0 7px 8px -4px rgba(137, 207, 255, 0.77);
+    font-family: 'PT Mono', Menlo, Monaco, Consolas, Courier New, monospace;
 }
 
 .ce-example__statusbar {
-  --toggler-size: 20px;
+    --toggler-size: 20px;
 }
 
 .ce-example__statusbar-toggler {
-  position: relative;
-  background: #7b8799;
-  border-radius: 20px;
-  padding: 2px;
-  width: calc(var(--toggler-size) * 2.2);
-  cursor: pointer;
-  user-select: none;
+    position: relative;
+    background: #7b8799;
+    border-radius: 20px;
+    padding: 2px;
+    width: calc(var(--toggler-size) * 2.2);
+    cursor: pointer;
+    user-select: none;
 }
 
 .ce-example__statusbar-toggler::before {
-  display: block;
-  content: '';
-  width: var(--toggler-size);
-  height: var(--toggler-size);
-  background: #fff;
-  border-radius: 50%;
-  transition: transform 100ms ease-in;
+    display: block;
+    content: '';
+    width: var(--toggler-size);
+    height: var(--toggler-size);
+    background: #fff;
+    border-radius: 50%;
+    transition: transform 100ms ease-in;
 }
 
 .ce-example__statusbar-toggler::after {
-  --moon-size: calc(var(--toggler-size) * 0.5);
-  content: '';
-  position: absolute;
-  top: 5px;
-  right: 5px;
-  height: var(--moon-size);
-  width: var(--moon-size);
-  box-shadow: calc(var(--moon-size) * 0.25 * -1) calc(var(--moon-size) * 0.18) 0 calc(var(--moon-size) * 0.05) white;
-  border-radius: 50%;
+    --moon-size: calc(var(--toggler-size) * 0.5);
+
+    content: '';
+    position: absolute;
+    top: 5px;
+    right: 5px;
+    height: var(--moon-size);
+    width: var(--moon-size);
+    box-shadow: calc(var(--moon-size) * 0.25 * -1) calc(var(--moon-size) * 0.18) 0 calc(var(--moon-size) * 0.05) white;
+    border-radius: 50%;
 }
 
-@media all and (max-width: 730px){
-  .ce-example__header,
-  .ce-example__content{
-    padding: 0 20px;
-  }
+@media all and (max-width: 730px) {
+    .ce-example__header,
+    .ce-example__content {
+        padding: 0 20px;
+    }
 }
 
 /**
  * JSON highlighter
  */
 .sc_attr {
-  color: rgb(148, 162, 192);
-}
-.sc_key {
-  color: rgb(190, 213, 255);
-}
-.sc_toolname {
-  color: rgb(15, 205, 251);
-}
-.sc_tag {
-  color: rgb(4, 131, 216);
-}
-.sc_bool {
-  color: rgb(247, 60, 173);
+    color: rgb(148, 162, 192);
 }
 
-.ce-example .ce-block:first-of-type h1.ce-header{
-  font-size: 50px;
+.sc_key {
+    color: rgb(190, 213, 255);
+}
+
+.sc_toolname {
+    color: rgb(15, 205, 251);
+}
+
+.sc_tag {
+    color: rgb(4, 131, 216);
+}
+
+.sc_bool {
+    color: rgb(247, 60, 173);
+}
+
+.ce-example .ce-block:first-of-type h1.ce-header {
+    font-size: 50px;
 }
 
 .ce-example-multiple {
-  display: grid;
-  grid-template-columns: calc(50% - 15px) calc(50% - 15px);
-  gap: 30px;
-  padding: 30px;
+    display: grid;
+    grid-template-columns: calc(50% - 15px) calc(50% - 15px);
+    gap: 30px;
+    padding: 30px;
 }
 
 .ce-example-multiple > div {
-  background: #fff;
-  border-radius: 7px;
-  padding: 30px;
+    background: #fff;
+    border-radius: 7px;
+    padding: 30px;
 }
 
-
 /**
  * Styles for the popup example page
  */
 .ce-example--popup {
-  height: 100vh;
-  display: flex;
-  flex-direction: column;
+    height: 100vh;
+    display: flex;
+    flex-direction: column;
 }
 
 .ce-example--popup .ce-example__content {
-  flex-grow: 2;
+    flex-grow: 2;
 }
 
 .ce-example-popup__overlay {
-  position: fixed;
-  top: 0;
-  bottom: 0;
-  left: 0;
-  right: 0;
-  background: #00000085;
+    position: fixed;
+    inset: 0;
+    background: #00000085;
 }
 
 .ce-example-popup__popup {
-  position: absolute;
-  left: 50%;
-  top: 50%;
-  transform: translate(-50%,-50%);
-  width: 800px;
-  max-width: 100%;
-  max-height: 90vh;
-  background: white;
-  padding: 20px;
-  border-radius: 8px;
-  overflow: auto;
-  box-sizing: border-box;
+    position: absolute;
+    left: 50%;
+    top: 50%;
+    transform: translate(-50%, -50%);
+    width: 800px;
+    max-width: 100%;
+    max-height: 90vh;
+    background: white;
+    padding: 20px;
+    border-radius: 8px;
+    overflow: auto;
+    box-sizing: border-box;
 }
 
-@media all and (max-width: 730px){
-  .ce-example-popup__popup {
-    top: 10px;
-    left: 10px;
-    width: calc(100% - 20px);
-    height: calc(100% - 20px);
-    transform: none;
-    max-height: none;
-
-  }
+@media all and (max-width: 730px) {
+    .ce-example-popup__popup {
+        top: 10px;
+        left: 10px;
+        width: calc(100% - 20px);
+        height: calc(100% - 20px);
+        transform: none;
+        max-height: none;
+    }
 }
 
 .show-block-boundaries .ce-block {
-  box-shadow: inset 0 0 0 1px #eff2f5;
+    box-shadow: inset 0 0 0 1px #eff2f5;
 }
 
 .show-block-boundaries .ce-block__content {
-  box-shadow: 0 0 0 1px rgba(224, 231, 241, 0.61) inset;
+    box-shadow: 0 0 0 1px rgba(224, 231, 241, 0.61) inset;
 }
+
 .show-block-boundaries #showBlocksBoundariesButton span,
 .thin-mode #enableThinModeButton span {
-  font-size: 0;
-  vertical-align: bottom;
+    font-size: 0;
+    vertical-align: bottom;
 }
 
 .show-block-boundaries #showBlocksBoundariesButton span::before,
 .thin-mode #enableThinModeButton span::before {
-  content: attr(data-toggled-text);
-  display: inline;
-  font-size: 13px;
+    content: attr(data-toggled-text);
+    display: inline;
+    font-size: 13px;
 }
 
-
-
 /**
  * Dark theme overrides
  */
 .dark-mode img {
-  opacity: 0.5;
+    opacity: 0.5;
 }
 
 .dark-mode .cdx-simple-image__picture--with-border,
 .dark-mode .cdx-input {
-  border-color: var(--color-border-light);
+    border-color: var(--color-border-light);
 }
 
 .dark-mode .ce-example__button {
-  box-shadow: 0 24px 18px -14px rgba(4, 154, 255, 0.24);
+    box-shadow: 0 24px 18px -14px rgba(4, 154, 255, 0.24);
 }
 
 .dark-mode .ce-example__output {
-  background-color: #17191f;
+    background-color: #17191f;
 }
 
 .dark-mode .inline-code {
-  background-color: rgba(53, 56, 68, 0.62);
-  color: #727683;
+    background-color: rgba(53, 56, 68, 0.62);
+    color: #727683;
 }
 
 .dark-mode a {
-  color: #959ba8;
+    color: #959ba8;
 }
 
 .dark-mode .ce-example__statusbar-toggler,
 .dark-mode .ce-example__statusbar-button {
-  background-color: #343842;
+    background-color: #343842;
 }
 
 .dark-mode .ce-example__statusbar-toggler::before {
-  transform: translateX(calc(var(--toggler-size) * 2.2 - var(--toggler-size)));
+    transform: translateX(calc(var(--toggler-size) * 2.2 - var(--toggler-size)));
 }
 
 .dark-mode .ce-example__statusbar-toggler::after {
-  content: '*';
-  right: auto;
-  left: 6px;
-  top: 7px;
-  color: #fff;
-  box-shadow: none;
-  font-size: 32px;
+    content: '*';
+    right: auto;
+    left: 6px;
+    top: 7px;
+    color: #fff;
+    box-shadow: none;
+    font-size: 32px;
 }
 
 .dark-mode.show-block-boundaries .ce-block,
 .dark-mode.show-block-boundaries .ce-block__content {
-  box-shadow: 0 0 0 1px rgba(128, 144, 159, 0.09) inset;
+    box-shadow: 0 0 0 1px rgba(128, 144, 159, 0.09) inset;
 }
 
-.dark-mode.thin-mode .ce-example__content{
-  border-color: var(--color-border-light);
+.dark-mode.thin-mode .ce-example__content {
+    border-color: var(--color-border-light);
 }
 
 .dark-mode .ce-example__statusbar-item:not(:last-of-type)::after {
-  color: var(--color-border-light);
+    color: var(--color-border-light);
 }
 
 .dark-mode .ce-block--selected .ce-block__content,
-.dark-mode ::selection{
-  background-color: rgba(57, 68, 84, 0.57);
+.dark-mode ::selection {
+    background-color: rgba(57, 68, 84, 0.57);
 }
 
 .dark-mode .ce-toolbox__button,
 .dark-mode .ce-toolbar__settings-btn,
 .dark-mode .ce-toolbar__plus {
-  color: inherit;
+    color: inherit;
 }
 
 .dark-mode .ce-stub {
-  opacity: 0.3;
+    opacity: 0.3;
 }
diff --git a/src/components/domIterator.ts b/src/components/domIterator.ts
index 5c3137b4..7a153495 100644
--- a/src/components/domIterator.ts
+++ b/src/components/domIterator.ts
@@ -40,19 +40,19 @@ export default class DomIterator {
    * @param {string} focusedCssClass - user-provided CSS-class that will be set in flipping process
    */
   constructor(
-    nodeList: HTMLElement[],
+    nodeList: HTMLElement[] | null | undefined,
     focusedCssClass: string
   ) {
-    this.items = nodeList || [];
+    this.items = nodeList ?? [];
     this.focusedCssClass = focusedCssClass;
   }
 
   /**
    * Returns Focused button Node
    *
-   * @returns {HTMLElement}
+   * @returns {HTMLElement | null}
    */
-  public get currentItem(): HTMLElement {
+  public get currentItem(): HTMLElement | null {
     if (this.cursor === -1) {
       return null;
     }
@@ -133,13 +133,13 @@ export default class DomIterator {
        * We need to do this to highlight "first" Tool correctly
        *
        * Order of Tools: [0] [1] ... [n - 1]
-       *   [0 = n] because of: n % n = 0 % n
+       * [0 = n] because of: n % n = 0 % n
        *
        * Direction 'right': for [0] the [n - 1] is a previous index
-       *   [n - 1] -> [0]
+       * [n - 1] -> [0]
        *
        * Direction 'left': for [n - 1] the [0] is a previous index
-       *   [n - 1] <- [0]
+       * [n - 1] <- [0]
        *
        * @type {number}
        */