diff --git a/browser/base/content/browser.css b/browser/base/content/browser.css
index 8a2a20280954eb9db144a723f477e7afc603fda3..a3b93a2e49c28a12b9bdc00ff290d768bba9e88b 100644
--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+@import url("chrome://global/skin/zen-global-shared.css");
+
 @namespace html url("http://www.w3.org/1999/xhtml");
 
 :root,
@@ -156,8 +158,7 @@ panelview:not([visible]) {
   flex: 100 100;
   max-width: 225px;
   min-width: var(--tab-min-width);
-  transition: min-width 100ms ease-out,
-              max-width 100ms ease-out;
+  transition: 100ms;
 }
 
 :root[uidensity=touch] .tabbrowser-tab:not([pinned]) {
@@ -1319,13 +1320,13 @@ printpreview-pagination:focus-within,
 
 
 #sidebar-box {
-  min-width: 14em;
+  min-width: 323px;
   max-width: 36em;
-  width: 18em;
+  width: 393px;
 }
 
 /* WebExtension Sidebars */
-#sidebar-box[sidebarcommand$="-sidebar-action"] > #sidebar-header > #sidebar-switcher-target > #sidebar-icon {
+#sidebar-box[sidebarcommand$="-sidebar-action"] #sidebar-header > #sidebar-switcher-target > #sidebar-icon {
   list-style-image: var(--webextension-menuitem-image, inherit);
   -moz-context-properties: fill;
   fill: currentColor;
@@ -1526,3 +1527,42 @@ toolbar[keyNav=true]:not([collapsed=true], [customizing=true]) toolbartabstop {
 /**
  * End Dialogs
  */
+
+/**
+ *
+ * ZEN OVERRIDES
+ */
+
+.content-prompt-dialog > .dialogOverlay {
+  align-content: start;
+}
+
+.dialogBox:not(.spotlightBox) {
+  border: 1px solid var(--zen-dialog-border-color);
+}
+
+#window-modal-dialog:not([zen-dialog-welcome-element="true"]) .dialogBox:not(.spotlightBox) {
+  transform: translateY(-9px);
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogBox:not(.spotlightBox) {
+  margin: 0 !important;
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"], 
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogOverlay,
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogFrame,
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogBox {
+  width: 100% !important;
+  height: 100% !important;
+  max-height: none !important;
+  max-width: none !important;
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"] {
+  --zen-welcome-dialog-space: 7px;
+  margin: 0 auto !important;
+  max-width: calc(100% - calc(var(--zen-welcome-dialog-space) * 2)) !important;
+  max-height: calc(100% - calc(var(--zen-welcome-dialog-space) * 2)) !important;
+  margin-top: var(--zen-welcome-dialog-space) !important;
+}