diff --git a/user.js b/user.js
index e526e39..132ba17 100644
--- a/user.js
+++ b/user.js
@@ -1,4 +1,4 @@
-// ** Theme Related Options ****************************************************
+// ** Theme GDefault Options ****************************************************
 // userchrome.css usercontent.css activate
 user_pref("toolkit.legacyUserProfileCustomizations.stylesheets", true);
 
@@ -26,6 +26,18 @@ user_pref("browser.newtabpage.activity-stream.improvesearch.handoffToAwesomebar"
 // Browser Theme Based Scheme - Will be activate 95 Above
 // user_pref("layout.css.prefers-color-scheme.content-override", 3);
 
+// ** Theme Related Options ****************************************************
+user_pref("userChrome.tab.sharePhoton",            true); // Original, Photon
+user_pref("userChrome.tab.shareProton",            true); // Original, Proton
+
+// user_pref("userChrome.tab.original",          true); // Original
+user_pref("userChrome.tab.photon",            true); // Photon
+// user_pref("userChrome.tab.proton",            true); // Proton
+user_pref("userChrome.tab.connect_to_window", true); // Original, Photon
+
+user_pref("userChrome.panel.proton", true); // Original, Proton
+user_pref("userChrome.panel.photon", true); // Photon
+
 // ** Useful Options ***********************************************************
 // Integrated calculator at urlbar
 user_pref("browser.urlbar.suggest.calculator", true);
diff --git a/userChrome.css b/userChrome.css
index 1ebb55c..1000177 100644
--- a/userChrome.css
+++ b/userChrome.css
@@ -55,22 +55,25 @@
 }
 
 /*= Remove Tab Border ========================================================*/
-/* Light Theme */
-#TabsToolbar:not([brighttext])
-  #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
-  > .tab-stack
-  > .tab-background {
-  border: unset !important; /* Nigtly 96:  1px solid var(--tab-line-color, rgba(128,128,142,0.9)); */
-}
+@supports -moz-bool-pref("userChrome.tab.connect_to_window") {
+  /* TARGET: original, photon */
+  /* Light Theme */
+  #TabsToolbar:not([brighttext])
+    #tabbrowser-tabs:not([noshadowfortests])
+    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    > .tab-stack
+    > .tab-background {
+    border: unset !important; /* Nigtly 96:  1px solid var(--tab-line-color, rgba(128,128,142,0.9)); */
+  }
 
-/* Dark Theme */
-#TabsToolbar[brighttext]
-  #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
-  > .tab-stack
-  > .tab-background:-moz-lwtheme {
-  border: unset !important; /* Nigtly 96: 1px solid var(--tab-line-color, rgba(128,128,142,0.9)) */
+  /* Dark Theme */
+  #TabsToolbar[brighttext]
+    #tabbrowser-tabs:not([noshadowfortests])
+    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    > .tab-stack
+    > .tab-background:-moz-lwtheme {
+    border: unset !important; /* Nigtly 96: 1px solid var(--tab-line-color, rgba(128,128,142,0.9)) */
+  }
 }
 
 /*= Light Weight Theme =======================================================*/
@@ -483,6 +486,20 @@
     --panel-separator-color: var(--win-border-color) !important;
   }
 
+  /*- Proton Tab Selected ----------------------------------------------------*/
+  @supports -moz-bool-pref("userChrome.tab.proton") {
+    :root:not(:-moz-lwtheme),
+    :root[lwt-default-theme-in-dark-mode] {
+      --win-proton-tab-selected-bgcolor: color-mix(in srgb, var(--win-bgcolor) 5%, var(--win-component-bgcolor));
+    }
+    :root:not(:-moz-lwtheme) {
+      --tab-selected-color: var(--win-proton-tab-selected-bgcolor) !important;
+    }
+    :root[lwt-default-theme-in-dark-mode] {
+      --lwt-selected-tab-background-color: var(--win-proton-tab-selected-bgcolor) !important;
+    }
+  }
+
   /*- Menu -------------------------------------------------------------------*/
   html#main-window menupopup:not(:-moz-lwtheme) {
     --menu-color: var(--win-text-color) !important;
@@ -762,6 +779,20 @@
     }
   }
 
+  /*- Proton Tab Selected ----------------------------------------------------*/
+  @supports -moz-bool-pref("userChrome.tab.proton") {
+    :root:not(:-moz-lwtheme),
+    :root[lwt-default-theme-in-dark-mode] {
+      --mac-proton-tab-selected-bgcolor: color-mix(in srgb, rgb(255, 255, 255) 20%, -moz-dialog);
+    }
+    :root:not(:-moz-lwtheme) {
+      --tab-selected-color: var(--mac-proton-tab-selected-bgcolor) !important;
+    }
+    :root[lwt-default-theme-in-dark-mode] {
+      --lwt-selected-tab-background-color: var(--mac-proton-tab-selected-bgcolor) !important;
+    }
+  }
+
   /*- Toolbar ----------------------------------------------------------------*/
   :root:not(:-moz-lwtheme) #navigator-toolbox,
   :root[lwt-default-theme-in-dark-mode] #navigator-toolbox {
@@ -819,7 +850,8 @@
   }
 
   /* Hard Coded */
-  :root[lwtheme-mozlightdark][lwt-default-theme-in-dark-mode] /* Legacy */
+  @supports -moz-bool-pref("userChrome.tab.connect_to_window") {
+    :root[lwtheme-mozlightdark][lwt-default-theme-in-dark-mode] /* Legacy */
     #tabbrowser-tabs:not([movingtab])
     > #tabbrowser-arrowscrollbox
     > .tabbrowser-tab
@@ -831,9 +863,9 @@
     > .tabbrowser-tab
     > .tab-stack
     > .tab-background[selected="true"] {
-    background: color-mix(in srgb, rgb(255, 255, 255) 15%, -moz-dialog) !important;
+      background: color-mix(in srgb, rgb(255, 255, 255) 15%, -moz-dialog) !important;
+    }
   }
-
   :root:not([customizing="true"]):not(:-moz-lwtheme) tab[visuallyselected] > stack::before,
   :root:not([customizing="true"]):not(:-moz-lwtheme) tab[visuallyselected] > stack::after,
   :root:not([customizing="true"])[lwt-default-theme-in-dark-mode] tab[visuallyselected] > stack::before,
@@ -1005,7 +1037,7 @@
   }
 }
 
-/*== Menu color =============================================================*/
+/*== Menu Color =============================================================*/
 html#main-window menupopup {
   /* is same as toolbar color https://github.com/mozilla/gecko-dev/blob/master/toolkit/themes/windows/global/global.css#L17-L67 */
   --menu-color: var(--arrowpanel-color, var(--in-content-page-color)) !important;
@@ -2702,11 +2734,21 @@ menuitem.openintabs-menuitem,
 
 /** Reduce Padding ************************************************************/
 /*= Root - Reduce Padding ====================================================*/
+@supports -moz-bool-pref("userChrome.tab.original") {
+  :root {
+    /* Tab Bar */
+    --proton-tab-block-margin: 2px !important; /* Original: 4px, Legacy */
+    --tab-block-margin: 2px !important; /* New version of --proton-tab-block-margin */
+  }
+}
+@supports -moz-bool-pref("userChrome.tab.photon") {
+  :root {
+    --proton-tab-block-margin: 0px !important; /* Original: 4px, Legacy */
+    --tab-block-margin: 0px !important; /* New version of --proton-tab-block-margin */
+    --tab-border-radius: 0px !important; /* Original: 4px */
+  }
+}
 :root {
-  /* Tab Bar */
-  --proton-tab-block-margin: 0px !important; /* Original: 4px, Legacy */
-  --tab-block-margin: 0px !important; /* New version of --proton-tab-block-margin */
-  --tab-border-radius: 0px !important; /* Original: 4px */
   --inline-tab-padding: 6px !important; /* Original: 8px */
 
   /* Panel */
@@ -2735,12 +2777,14 @@ menuitem.openintabs-menuitem,
 }
 
 /* Fix Tab bar button radious */
+@supports -moz-bool-pref("userChrome.tab.photon") {
 #TabsToolbar .toolbarbutton-1 > .toolbarbutton-icon,
 #TabsToolbar .toolbarbutton-1 > .toolbarbutton-text,
 #TabsToolbar .toolbarbutton-1 > .toolbarbutton-badge-stack,
 .tab-close-button {
   --tab-border-radius: 4px !important;
 }
+}
 
 /*= Tab Bar - Reduce Width, Show more tabs ===================================*/
 /* for First Tab Space */
@@ -2775,11 +2819,20 @@ menuitem.openintabs-menuitem,
   padding-right: var(--newtab-button-width-padding) !important;
 }
 
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+#tabbrowser-tabs[haspinnedtabs]:not([positionpinnedtabs])
+  > #tabbrowser-arrowscrollbox
+  > .tabbrowser-tab[first-visible-unpinned-tab] {
+  margin-inline-start: 1px !important;
+}
+}
+@supports -moz-bool-pref("userChrome.tab.photon") {
 #tabbrowser-tabs[haspinnedtabs]:not([positionpinnedtabs])
   > #tabbrowser-arrowscrollbox
   > .tabbrowser-tab[first-visible-unpinned-tab] {
   margin-inline-start: 0 !important;
 }
+}
 
 :root:not([uidensity="touch"]) #tabbrowser-arrowscrollbox {
   --scrollbtn-inner-padding: 1px;
@@ -2800,17 +2853,34 @@ menuitem.openintabs-menuitem,
 }
 
 /* Tab - Max Size */
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+:root {
+  --tab-max-width: 240px;
+}
+}
+@supports -moz-bool-pref("userChrome.tab.photon") {
 :root {
   --tab-max-width: 225px;
 }
+}
 .tabbrowser-tab[fadein]:not([pinned]):not([style*="max-width"]) {
   max-width: var(--tab-max-width) !important; /* Original: 225px */
 }
 
 /* neighbouring tabs should "pinch" together */
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+.tabbrowser-tab {
+  padding-inline: 1px !important;
+}
+.tabbrowser-tab:not([last-visible-tab]) {
+  margin-inline-end: -0.5px !important;
+}
+}
+@supports -moz-bool-pref("userChrome.tab.photon") {
 .tabbrowser-tab {
   padding-inline: 0 !important;
 }
+}
 
 /*= Tab Bar - Reduce Height, Show more contents ==============================*/
 /* for Extra Drag Space */
@@ -2826,6 +2896,20 @@ menuitem.openintabs-menuitem,
 }
 
 /* Toolbar Height */
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+:root:not([uidensity="touch"]) #TabsToolbar {
+  --toolbarbutton-inner-padding: 9px; /* Original: calc((var(--tab-min-height) - 16px) / 2) = 10px */
+}
+
+:root:not([uidensity]) #TabsToolbar {
+  --tab-min-height: 36px !important; /* 38px -> 36px */
+}
+:root[uidensity="compact"] #TabsToolbar {
+  --tab-min-height: 29px !important; /* 36px -> 29px */
+}
+}
+
+@supports -moz-bool-pref("userChrome.tab.photon") {
 #TabsToolbar {
   --tab-min-height: 33px !important;
   --toolbarbutton-inner-padding: unset !important;
@@ -2847,6 +2931,31 @@ menuitem.openintabs-menuitem,
 .tab-content {
   margin-top: 0 !important;
 }
+}
+
+@supports -moz-bool-pref("userChrome.tab.original") {
+  .toolbar-items,
+  .tabbrowser-tab {
+    --tabbar-max-height: 38px;
+    max-height: calc(var(--tabbar-max-height) + var(--space-above-tabbar));
+  }
+  :root[uidensity="compact"] .toolbar-items,
+  :root[uidensity="compact"] .tabbrowser-tab {
+    --tabbar-max-height: 36px;
+  }
+  :root[uidensity="touch"] .toolbar-items,
+  :root[uidensity="touch"] .tabbrowser-tab {
+    --tabbar-max-height: 45px;
+  }
+}
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  :root:not([uidensity]) #TabsToolbar {
+    --tab-min-height: 36px !important; /* 38px -> 36px */
+  }
+  :root[uidensity="compact"] #TabsToolbar {
+    --tab-min-height: 29px !important; /* 36px -> 29px */
+  }
+}
 
 /* Scroll Button - Size Fix */
 :root #tabbrowser-arrowscrollbox {
@@ -3136,45 +3245,49 @@ menupopup > menu {
 }
 
 /** Tab Bar - Connect to window ***********************************************/
-.tab-background {
-  border-radius: var(--tab-border-radius) var(--tab-border-radius) 0px 0px !important;
-  margin-bottom: 0px !important;
-}
+@supports -moz-bool-pref("userChrome.tab.connect_to_window") {
+  .tab-background {
+    border-radius: var(--tab-border-radius) var(--tab-border-radius) 0px 0px !important;
+    margin-bottom: 0px !important;
+  }
 
-.tab-content {
-  margin-top: var(--tab-block-margin);
-}
+  .tab-content {
+    margin-top: var(--tab-block-margin);
+  }
 
-.tab-stack {
-  margin-top: 0px !important;
-  margin-bottom: 0px !important;
-}
+  .tab-stack {
+    margin-top: 0px !important;
+    margin-bottom: 0px !important;
+  }
 
-/* Remove line at Toolbar's top */
-#tabbrowser-tabs {
-  z-index: 1 !important;
-}
-#tabbrowser-arrowscrollbox[overflowing] .tabbrowser-tab[pinned]:is([visuallyselected], [multiselected]) {
-  overflow: hidden;
+  /* Remove line at Toolbar's top */
+  #tabbrowser-tabs {
+    z-index: 1 !important;
+  }
+  #tabbrowser-arrowscrollbox[overflowing] .tabbrowser-tab[pinned]:is([visuallyselected], [multiselected]) {
+    overflow: hidden;
+  }
 }
 
 /** Selected Tab - Color like toolbar *****************************************/
-:root:not(:-moz-lwtheme) {
-  /* Fix for windows's system default theme. Using --toolbar-bgcolor fallback */
-  --tab-selected-bgcolor: unset !important; /* Original: rgb(255,255,255); */
-}
-#tabbrowser-tabs:not([movingtab])
-  > #tabbrowser-arrowscrollbox
-  > .tabbrowser-tab
-  > .tab-stack
-  > .tab-background[selected="true"]:-moz-lwtheme {
-  /* Original: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none)
+@supports -moz-bool-pref("userChrome.tab.connect_to_window") {
+  :root:not(:-moz-lwtheme) {
+    /* Fix for windows's system default theme. Using --toolbar-bgcolor fallback */
+    --tab-selected-bgcolor: unset !important; /* Original: rgb(255,255,255); */
+  }
+  #tabbrowser-tabs:not([movingtab])
+    > #tabbrowser-arrowscrollbox
+    > .tabbrowser-tab
+    > .tab-stack
+    > .tab-background[selected="true"]:-moz-lwtheme {
+    /* Original: linear-gradient(var(--lwt-selected-tab-background-color, transparent), var(--lwt-selected-tab-background-color, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none)
  */
-  background-image: linear-gradient(transparent, transparent),
-    linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
+    background-image: linear-gradient(transparent, transparent),
+      linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
+  }
 }
 
-/* Multi Selected Color */
+/** Multi Selected Color - More Contrast **************************************/
 #tabbrowser-tabs:not([movingtab])
   > #tabbrowser-arrowscrollbox
   > .tabbrowser-tab
@@ -3194,7 +3307,104 @@ menupopup > menu {
   opacity: 0.15;
 }
 
+/** Selected Tab - Box Shadow *************************************************/
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #TabsToolbar[brighttext]
+    #tabbrowser-tabs:not([noshadowfortests])
+    .tabbrowser-tab[visuallyselected="true"]:not(:focus)
+    > .tab-stack
+    > .tab-background:-moz-lwtheme {
+    /* Origina: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
+       Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
+    box-shadow: 0 0 1px var(--toolbar-color) !important;
+  }
+  #TabsToolbar[brighttext]
+    #tabbrowser-tabs:not([noshadowfortests])
+    .tabbrowser-tab[multiselected]:not([visuallyselected])
+    > .tab-stack
+    > .tab-background:-moz-lwtheme {
+    box-shadow: 0 0 1px color-mix(in srgb, var(--toolbar-color) 80%, transparent) !important;
+  }
+
+  /* Pinned Tab - tabbrowser-arrowscrollbox overflowing */
+  #tabbrowser-tabs[positionpinnedtabs] > #tabbrowser-arrowscrollbox > .tabbrowser-tab[pinned] {
+    z-index: 0 !important;
+  }
+}
+
+/** Selected Tab - Bottom Rounded Corner **************************************/
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #tabbrowser-tabs {
+    --tab-corner-rounding: 3px; /* 10px looks about like chromium - 17px looks close to Australis tabs */
+    --tab-corner-padding: 0px;
+    --tab-corner-position: calc(var(--tab-corner-padding) - var(--tab-corner-rounding));
+  }
+
+  :root:not([customizing="true"]) tab[visuallyselected] > stack::before,
+  :root:not([customizing="true"]) tab[visuallyselected] > stack::after {
+    content: "" !important;
+
+    /* Box */
+    display: block !important;
+    position: absolute !important;
+    z-index: 1 !important;
+
+    /* Shape */
+    width: var(--tab-corner-rounding) !important;
+    height: 100% !important;
+
+    /* Color */
+    fill: var(--toolbar-bgcolor) !important;
+    stroke: var(--tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9))) !important;
+    -moz-context-properties: fill, stroke !important;
+
+    /* Image */
+    background-size: var(--tab-corner-rounding);
+    background-repeat: no-repeat;
+    background-position-y: bottom;
+  }
+  :root:not([customizing="true"]) #TabsToolbar[brighttext] tab[visuallyselected] > stack::before,
+  :root:not([customizing="true"]) #TabsToolbar[brighttext] tab[visuallyselected] > stack::after {
+    /* As Selected Tab - Box Shadow */
+    stroke: var(--toolbar-color) !important;
+  }
+
+  tab[visuallyselected] > stack::before {
+    left: var(--tab-corner-position) !important;
+    background-image: url("./icons/tab-bottom-corner-left.svg");
+  }
+  tab[visuallyselected] > stack::after {
+    left: auto;
+    right: var(--tab-corner-position);
+    background-image: url("./icons/tab-bottom-corner-right.svg");
+  }
+
+  @media (-moz-gtk-csd-available) {
+    /* Fill color for GTK */
+    :root:not([customizing="true"]):not([lwtheme="true"]) tab[visuallyselected] > stack::before,
+    :root:not([customizing="true"]):not([lwtheme="true"]) tab[visuallyselected] > stack::after {
+      /* As GTK Toolbar's background-color + backround-image
+       * --toolbar-non-lwt-bgcolor: -moz-dialog;
+       * --toolbar-non-lwt-bgimage: linear-gradient(rgba(255,255,255,.15), rgba(255,255,255,.15));
+       */
+      fill: color-mix(in srgb, rgb(255, 255, 255) 15%, -moz-dialog) !important;
+      stroke: transparent !important;
+    }
+    :root:not([customizing="true"]):not([lwtheme="true"])
+      #TabsToolbar[brighttext]
+      tab[visuallyselected]
+      > stack::before,
+    :root:not([customizing="true"]):not([lwtheme="true"])
+      #TabsToolbar[brighttext]
+      tab[visuallyselected]
+      > stack::after {
+      stroke: transparent !important;
+    }
+  }
+}
+
 /** Selected Tab - Photon like contextline ************************************/
+@supports -moz-bool-pref("userChrome.tab.photon") {
 :root[lwtheme-mozlightdark] #tabbrowser-tabs {
   --tab-line-color: rgb(10, 132, 255) !important;
 }
@@ -3272,8 +3482,151 @@ menupopup > menu {
 .tabbrowser-tab[usercontextid] > .tab-stack > .tab-background > .tab-context-line {
   margin: unset !important;
 }
+}
 
-/** Unselected Tab - Divide line **********************************************/
+/** Unselected Tab - Dynamic Separator ****************************************/
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #tabbrowser-arrowscrollbox {
+    position: absolute;
+  }
+}
+
+@supports -moz-bool-pref("userChrome.tab.original") {
+  .tab-background::before,
+  #tabs-newtab-button::before {
+    /* Box Model */
+    content: "";
+    display: block;
+    position: absolute;
+
+    /* Position */
+    top: 50%;
+    transform: translateX(-2.5px) translateY(calc(-50% + 1px));
+
+    /* Bar shape */
+    width: 1px;
+    height: 20px;
+
+    /* Bar Color */
+    opacity: 0;
+    background-color: var(--toolbarseparator-color);
+  }
+}
+
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  .tab-background::before,
+  #tabbrowser-arrowscrollbox:not([overflowing])
+    .tabbrowser-tab:not([visuallyselected], [multiselected], :hover)[last-visible-tab]
+    .tab-background::after {
+    /* Box Model */
+    content: "";
+    display: block;
+    position: absolute;
+    top: 50%;
+
+    /* Bar shape */
+    width: 1px;
+    height: 20px;
+
+    /* Bar Color */
+    opacity: 0;
+    background-color: var(--toolbarseparator-color);
+  }
+}
+
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  .tab-background::before {
+    transform: translateX(-2.5px) translateY(calc(-50% + 1px)) !important;
+  }
+  .tabbrowser-tab[last-visible-tab] .tab-background::after {
+    right: 0;
+    transform: translateX(1.5px) translateY(calc(-50% + 1px)) !important;
+  }
+}
+
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+.tabbrowser-tab:not([visuallyselected], [multiselected], :hover, :first-child) .tab-background::before {
+  opacity: var(--tab-separator-opacity);
+}
+}
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #tabs-newtab-button:not(:hover, [open])::before {
+    opacity: var(--tab-separator-opacity);
+  }
+}
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  #tabbrowser-arrowscrollbox:not([overflowing]) .tabbrowser-tab[first-visible-unpinned-tab] .tab-background::before,
+  #tabbrowser-arrowscrollbox:not([overflowing])
+    .tabbrowser-tab:not([visuallyselected], [multiselected], :hover)[last-visible-tab]
+    .tab-background::after {
+    opacity: var(--tab-separator-opacity);
+  }
+}
+
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+#navigator-toolbox:not([movingtab])
+  .tabbrowser-tab[first-visible-unpinned-tab]:is([visuallyselected], [multiselected], :hover)
+  .tab-background::before,
+#navigator-toolbox:not([movingtab])
+  #tabbrowser-arrowscrollbox[overflowing]
+  tab.tabbrowser-tab[first-visible-unpinned-tab]
+  .tab-background::before {
+  opacity: 0 !important;
+}
+}
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #navigator-toolbox:not([movingtab])
+    .tabbrowser-tab:is([visuallyselected], [multiselected], :hover)
+    + .tabbrowser-tab
+    .tab-background::before,
+  #navigator-toolbox:not([movingtab])
+    .tabbrowser-tab:is([visuallyselected], [multiselected], :hover)
+    ~ .tabbrowser-tab[afterhovered]
+    .tab-background::before,
+  #navigator-toolbox:not([movingtab])
+    .tabbrowser-tab[last-visible-tab]:is([visuallyselected], [multiselected], :hover)
+    ~ #tabs-newtab-button::before {
+    opacity: 0 !important;
+  }
+}
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  .tabbrowser-tab:is([visuallyselected], [multiselected], :hover)
+    + .tabbrowser-tab:not([visuallyselected])
+    .tab-background::before {
+    opacity: 0 !important;
+  }
+}
+
+/* Animate */
+@media (prefers-reduced-motion: no-preference) {
+  @supports -moz-bool-pref("userChrome.tab.shareProton") {
+  .tab-background::before {
+    transition: opacity 0.2s var(--animation-easing-function); /* cubic-bezier(.07, .95, 0, 1) */
+  }
+  }
+  @supports -moz-bool-pref("userChrome.tab.original") {
+    #tabs-newtab-button::before {
+      transition: opacity 0.2s var(--animation-easing-function); /* cubic-bezier(.07, .95, 0, 1) */
+    }
+  }
+  @supports -moz-bool-pref("userChrome.tab.proton") {
+    #tabbrowser-arrowscrollbox:not([overflowing])
+      .tabbrowser-tab:not([visuallyselected], [multiselected], :hover)[last-visible-tab]
+      .tab-background::after {
+      transition: opacity 0.2s var(--animation-easing-function); /* cubic-bezier(.07, .95, 0, 1) */
+    }
+  }
+}
+
+/* Latest Tab & New tab margin */
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+#tabbrowser-arrowscrollbox:not([overflowing]) .tabbrowser-tab[last-visible-tab] {
+  margin-inline-end: 1px !important;
+}
+}
+
+/** Unselected Tab - Static Separator *****************************************/
+@supports -moz-bool-pref("userChrome.tab.photon") {
 .tabbrowser-tab[first-visible-tab]::before,
 .tabbrowser-tab::after,
 #tabbrowser-tabs[movingtab] > #tabbrowser-arrowscrollbox > .tabbrowser-tab[visuallyselected]::before {
@@ -3311,8 +3664,76 @@ menupopup > menu {
   margin-bottom: 0 !important;
   opacity: 1 !important;
 }
+}
+
+/* New tab button - Looks like tab ********************************************/
+@supports -moz-bool-pref("userChrome.tab.original") {
+  #tabs-newtab-button {
+    /* Original:
+    margin: 0 0 var(--tabs-navbar-shadow-size) !important
+    => Can't ovrride style. Therefore, we should approach it by bypass.
+    */
+    --tabs-navbar-shadow-size: -1px; /* Original: 1px */
+    --tabs-navbar-original-shadow-size: 1px;
+    --tab-corner-rounding: 4px; /* Hardcorded */
+
+    /* Size */
+    -moz-box-align: stretch !important;
+    padding-top: var(--tab-block-margin) !important;
+
+    /* Corner Rounding Image */
+    --newtab-position: calc((var(--tab-corner-rounding) / 2) * -1);
+    background-image: url("./icons/tab-bottom-corner-left.svg"), url("./icons/tab-bottom-corner-right.svg");
+    background-repeat: no-repeat;
+    background-position: left var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size),
+      right var(--newtab-position) bottom var(--tabs-navbar-original-shadow-size);
+    background-size: var(--tab-corner-rounding);
+
+    /* Corner Rounding Color */
+    fill: transparent !important;
+    -moz-context-properties: fill !important;
+  }
+
+  /* Corner Rounding Color */
+  #tabs-newtab-button:hover {
+    fill: var(--toolbarbutton-hover-background) !important;
+  }
+  #tabs-newtab-button:hover:active {
+    fill: var(--toolbarbutton-active-background) !important;
+  }
+  @media (-moz-windows-accent-color-in-titlebar) {
+    :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover,
+    :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover {
+      fill: color-mix(
+        in srgb,
+        -moz-accent-color-foreground 10%,
+        transparent
+      ) !important; /* Hardcorded for compatibility */
+    }
+    :root[tabsintitlebar]:not(:-moz-window-inactive, :-moz-lwtheme) #tabs-newtab-button:hover:active,
+    :root[tabsintitlebar][lwt-default-theme-in-dark-mode]:not(:-moz-window-inactive) #tabs-newtab-button:hover:active {
+      fill: color-mix(
+        in srgb,
+        -moz-accent-color-foreground 15%,
+        transparent
+      ) !important; /* Hardcorded for compatibility */
+    }
+  }
+
+  /* '+'Icon */
+  #tabs-newtab-button .toolbarbutton-icon {
+    border-radius: var(--tab-border-radius) var(--tab-border-radius) 0 0 !important; /* Original: var(--tab-border-radius) */
+
+    padding: calc(var(--toolbarbutton-inner-padding) - (var(--tab-block-margin) / 4)) var(--toolbarbutton-inner-padding)
+      calc(var(--toolbarbutton-inner-padding) + (var(--tab-block-margin) / 4) + var(--tabs-navbar-original-shadow-size)) !important;
+    -moz-context-properties: fill, fill-opacity;
+    fill: var(--toolbarbutton-icon-fill);
+    fill-opacity: var(--toolbarbutton-icon-fill-opacity);
+  }
+}
 
 /** New tab button - Smaller button *******************************************/
+@supports -moz-bool-pref("userChrome.tab.photon") {
 #tabs-newtab-button > .toolbarbutton-icon {
   margin-left: 1px;
 
@@ -3325,6 +3746,21 @@ menupopup > menu {
 :root[uidensity="touch"] #tabs-newtab-button > .toolbarbutton-icon {
   --toolbarbutton-inner-padding: 9px; /* Photon: 9px */
 }
+}
+
+/* New tab button - Smaller button ********************************************/
+@supports -moz-bool-pref("userChrome.tab.proton") {
+  :root:not([uidensity="touch"]) #tabs-newtab-button > .toolbarbutton-icon {
+    --toolbarbutton-inner-padding: calc((var(--tab-min-height) - 16px) / 2 - 1px);
+  }
+
+  :root:not([uidensity="compact"]) #tabs-newtab-button > .toolbarbutton-icon {
+    margin-left: 2px;
+  }
+  :root[uidensity="compact"] #tabs-newtab-button > .toolbarbutton-icon {
+    margin-left: 1px;
+  }
+}
 
 /* Unloaded Tab - Contents Opacity ********************************************/
 #tabbrowser-tabs .tabbrowser-tab[pending] .tab-content {
@@ -3548,6 +3984,12 @@ menupopup > menu {
 }
 
 /** Container Tab - Color line at icon's bottom *******************************/
+@supports -moz-bool-pref("userChrome.tab.shareProton") {
+.tab-context-line {
+  display: none;
+}
+}
+
 .tab-content:not([titlechanged])::before {
   /* Box Model */
   content: "";
@@ -3821,7 +4263,10 @@ menupopup > menu {
 :root {
   --arrowpanel-menublank-padding: calc(var(--arrowpanel-menuicon-padding) * 2 + 8px) !important;
   --arrowpanel-menuimageblank-padding: calc(var(--arrowpanel-menuitem-padding) - 2px) !important;
+}
 
+@supports -moz-bool-pref("userChrome.panel.photon") {
+:root {
   /* Blank Menu Left Padding */
   --arrowpanel-menuimageblank-padding-horizontal: calc(var(--arrowpanel-menublank-padding) - 3px);
   --arrowpanel-menuitemblank-padding: calc(var(--arrowpanel-menuitem-padding) + 1px);
@@ -3846,6 +4291,7 @@ menupopup > menu {
   );
   --arrowpanel-menuitemblank-padding: calc(var(--arrowpanel-menuitem-padding) + 1px);
 }
+}
 
 #downloadsHistory .button-text,
 .subviewbutton > .toolbarbutton-text {
@@ -3939,6 +4385,12 @@ menupopup > menu {
   background-image: var(--avatar-image-url) !important;
 }
 
+@supports -moz-bool-pref("userChrome.panel.proton") {
+  #appMenu-new-tab-button2 {
+    list-style-image: url("chrome://browser/skin/new-tab.svg");
+  }
+}
+@supports -moz-bool-pref("userChrome.panel.photon") {
 #appMenu-new-tab-button2,           /* Seperate */
   #appMenu-passwords-button,          /* Seperate */
   #appMenu-extensions-themes-button,
@@ -3954,6 +4406,7 @@ menupopup > menu {
 #appMenu-zoom-controls2 {
   padding-inline-start: var(--arrowpanel-menuimageblank-padding-horizontal) !important;
 }
+}
 
 #appMenu-new-window-button2 {
   list-style-image: url("chrome://browser/skin/window.svg");
@@ -3971,14 +4424,45 @@ menupopup > menu {
 #appMenu-downloads-button {
   list-style-image: url("chrome://browser/skin/downloads/downloads.svg");
 }
+@supports -moz-bool-pref("userChrome.panel.proton") {
+  #appMenu-passwords-button {
+    list-style-image: url("chrome://browser/skin/login.svg");
+  }
+  #appMenu-extensions-themes-button {
+    list-style-image: url("chrome://mozapps/skin/extensions/extension.svg");
+  }
+}
 
 #appMenu-print-button2 {
   list-style-image: url("chrome://global/skin/icons/print.svg");
 }
+@supports -moz-bool-pref("userChrome.panel.proton") {
+  #appMenu-save-file-button2 {
+    list-style-image: url("chrome://browser/skin/save.svg");
+  }
+  #appMenu-find-button2 {
+    list-style-image: url("chrome://global/skin/icons/search-glass.svg");
+  }
+  #appMenu-zoom-controls2::before {
+    content: url("./icons/screenshot.svg");
+  }
+}
 
 #appMenu-settings-button {
   list-style-image: url("chrome://global/skin/icons/settings.svg");
 }
+@supports -moz-bool-pref("userChrome.panel.proton") {
+  #appMenu-more-button2 {
+    list-style-image: url("chrome://browser/skin/ion.svg");
+  }
+  #appMenu-help-button2 {
+    list-style-image: url("chrome://global/skin/icons/help.svg");
+  }
+
+  #appMenu-quit-button2 {
+    list-style-image: url("./icons/quit.svg");
+  }
+}
 
 /*= Panel - Account ==========================================================*/
 #PanelUI-fxa-menu-connect-device-button .toolbarbutton-icon,