diff --git a/toolkit/themes/shared/aboutReader.css b/toolkit/themes/shared/aboutReader.css
index 6e4206e2939f04639ca20f8985d2ab97b571e857..27b6dbcf9cc77d7454461e056ca91ba5055aff19 100644
--- a/toolkit/themes/shared/aboutReader.css
+++ b/toolkit/themes/shared/aboutReader.css
@@ -912,3 +912,43 @@ pre code {
   display: block;
   overflow: auto;
 }
+
+/* Zen Overrides */
+
+.toolbar {
+  border: none !important;
+  padding: 0 !important;
+  box-shadow: none !important;
+}
+
+.toolbar-button {
+  border-radius: 50% !important;
+}
+
+.open>.dropdown-popup {
+  border: 1px solid light-dark(#00000033, #ffffff33) !important;
+  border-radius: 12px !important;
+}
+
+.font-type-buttons > label {
+  background-color: transparent !important;
+}
+
+.radiorow>label {
+  border-radius: 8px !important;
+}
+
+.buttonrow > button {
+  opacity: .6;
+}
+
+.buttonrow > button:enabled:hover,
+.buttonrow > button:enabled:hover:active {
+  background-color: transparent !important;
+  opacity: 1;
+}
+
+.radiorow>input[type=radio]:focus-visible+label::after,
+.radiorow>label:hover::after {
+  border: none !important;
+}