diff --git a/styles.css b/styles.css
index f2d39eb..c9cbcc8 100644
--- a/styles.css
+++ b/styles.css
@@ -63,10 +63,13 @@ body {
   padding: 1.5rem;
 }
 
+/* Segmented control: both options joined in one rounded container,
+   with the active segment filled. */
 .theme-toggle {
-  display: flex;
-  gap: 0.5rem;
-  border: none;
+  display: inline-flex;
+  border: 2px solid var(--button-bg);
+  border-radius: 999px;
+  overflow: hidden;
   margin: 0;
   padding: 0;
 }
@@ -75,19 +78,22 @@ body {
   font-family: inherit;
   font-size: 0.9rem;
   font-weight: 600;
-  padding: 0.5rem 1rem;
-  border: 2px solid var(--button-bg);
-  border-radius: 999px;
+  padding: 0.5rem 1.1rem;
+  border: none;
   background: transparent;
   color: var(--text);
   cursor: pointer;
   transition: background 0.2s ease, color 0.2s ease;
 }
 
+/* Divider between the two segments. */
+.theme-button + .theme-button {
+  border-left: 2px solid var(--button-bg);
+}
+
 .theme-button[aria-pressed="true"] {
   background: var(--button-active-bg);
   color: var(--button-active-text);
-  border-color: var(--button-active-bg);
 }
 
 .stage {