diff --git a/kjvstudy_org/static/css/family-tree-expansions.css b/kjvstudy_org/static/css/family-tree-expansions.css
index a9a5d7a..1be0a84 100644
--- a/kjvstudy_org/static/css/family-tree-expansions.css
+++ b/kjvstudy_org/static/css/family-tree-expansions.css
@@ -1087,38 +1087,38 @@
     }
 }
 
-/* Dark mode support */
+/* Dark mode support (only when explicit theme not set to light) */
 @media (prefers-color-scheme: dark) {
-    .family-search-container,
-    .family-analytics-container {
+    html:not([data-theme="light"]) .family-search-container,
+    html:not([data-theme="light"]) .family-analytics-container {
         background: #2d3436;
         border-color: #636e72;
         color: #ddd;
     }
-    
-    .search-input {
+
+    html:not([data-theme="light"]) .search-input {
         background: #2d3436;
         border-color: #636e72;
         color: #ddd;
     }
-    
-    .search-filters,
-    .breadcrumb-navigation,
-    .quick-navigation {
+
+    html:not([data-theme="light"]) .search-filters,
+    html:not([data-theme="light"]) .breadcrumb-navigation,
+    html:not([data-theme="light"]) .quick-navigation {
         background: #2d3436;
         border-color: #636e72;
     }
-    
-    .stat-card,
-    .chart-insights,
-    .insight-card,
-    .metric-item {
+
+    html:not([data-theme="light"]) .stat-card,
+    html:not([data-theme="light"]) .chart-insights,
+    html:not([data-theme="light"]) .insight-card,
+    html:not([data-theme="light"]) .metric-item {
         background: #2d3436;
         border-color: #636e72;
         color: #ddd;
     }
-    
-    .analytics-header {
+
+    html:not([data-theme="light"]) .analytics-header {
         background: linear-gradient(135deg, #0984e3 0%, #74b9ff 100%);
     }
 }
diff --git a/kjvstudy_org/static/tufte.css b/kjvstudy_org/static/tufte.css
index 764e4a0..9a58af0 100644
--- a/kjvstudy_org/static/tufte.css
+++ b/kjvstudy_org/static/tufte.css
@@ -52,29 +52,31 @@ body {
     counter-reset: sidenote-counter;
 }
 
-/* Adds dark mode - system preference */
+/* Adds dark mode - system preference (only when explicit theme not set to light) */
 @media (prefers-color-scheme: dark) {
-    body {
+    html:not([data-theme="light"]) body {
         background-color: #151515;
         color: #ddd;
     }
 
-    .sidenote,
-    .marginnote {
+    html:not([data-theme="light"]) .sidenote,
+    html:not([data-theme="light"]) .marginnote {
         background-color: #151515;
         color: #ddd;
     }
 
-    a:link,
-    a:visited {
+    html:not([data-theme="light"]) a:link,
+    html:not([data-theme="light"]) a:visited {
         color: #aaa;
     }
 
-    hr {
+    html:not([data-theme="light"]) hr {
         border-top-color: #444;
     }
 
-    h1, h2, h3 {
+    html:not([data-theme="light"]) h1,
+    html:not([data-theme="light"]) h2,
+    html:not([data-theme="light"]) h3 {
         color: #ddd;
     }
 }
diff --git a/kjvstudy_org/templates/base.html b/kjvstudy_org/templates/base.html
index 4123136..de78d6d 100644
--- a/kjvstudy_org/templates/base.html
+++ b/kjvstudy_org/templates/base.html
@@ -252,7 +252,7 @@
         }
 
         @media (prefers-color-scheme: dark) {
-            .verse-tooltip:not([data-theme]) {
+            html:not([data-theme="light"]) .verse-tooltip {
                 background: #2a2a2a;
                 border-color: #444;
                 box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
diff --git a/kjvstudy_org/templates/chapter_interlinear.html b/kjvstudy_org/templates/chapter_interlinear.html
index b7f030c..85c7a50 100644
--- a/kjvstudy_org/templates/chapter_interlinear.html
+++ b/kjvstudy_org/templates/chapter_interlinear.html
@@ -379,52 +379,53 @@
     border-bottom-color: #333;
 }
 
+/* Only apply OS dark mode when explicit theme is not set to light */
 @media (prefers-color-scheme: dark) {
-    .word-original {
+    html:not([data-theme="light"]) .word-original {
         color: #eee;
     }
 
-    .word-unit:hover .word-original {
+    html:not([data-theme="light"]) .word-unit:hover .word-original {
         color: #fff;
     }
 
-    .word-unit:hover {
+    html:not([data-theme="light"]) .word-unit:hover {
         background: #2a2a2a;
         border-color: #444;
     }
 
-    .word-unit.expanded {
+    html:not([data-theme="light"]) .word-unit.expanded {
         background: #1a2e1a;
         border-color: #4a7c59;
     }
 
-    .word-detail {
+    html:not([data-theme="light"]) .word-detail {
         background: #222;
         border-color: #444;
     }
 
-    .word-detail-original {
+    html:not([data-theme="light"]) .word-detail-original {
         color: #eee;
     }
 
-    .word-detail-value {
+    html:not([data-theme="light"]) .word-detail-value {
         color: #ddd;
     }
 
-    .word-detail-definition {
+    html:not([data-theme="light"]) .word-detail-definition {
         color: #bbb;
         border-top-color: #444;
     }
 
-    .word-detail-header {
+    html:not([data-theme="light"]) .word-detail-header {
         border-bottom-color: #444;
     }
 
-    .verse-text {
+    html:not([data-theme="light"]) .verse-text {
         color: #ccc;
     }
 
-    .verse-section {
+    html:not([data-theme="light"]) .verse-section {
         border-bottom-color: #333;
     }
 }
diff --git a/kjvstudy_org/templates/verse.html b/kjvstudy_org/templates/verse.html
index 48520fd..891f852 100644
--- a/kjvstudy_org/templates/verse.html
+++ b/kjvstudy_org/templates/verse.html
@@ -501,48 +501,49 @@
     border-bottom-color: #444;
 }
 
+/* Only apply OS dark mode when explicit theme is not set to light */
 @media (prefers-color-scheme: dark) {
-    .word-original {
+    html:not([data-theme="light"]) .word-original {
         color: #eee;
     }
 
-    .word-unit:hover .word-original {
+    html:not([data-theme="light"]) .word-unit:hover .word-original {
         color: #fff;
     }
 
-    .word-unit:hover {
+    html:not([data-theme="light"]) .word-unit:hover {
         background: #2a2a2a;
         border-color: #444;
     }
 
-    .word-unit.expanded {
+    html:not([data-theme="light"]) .word-unit.expanded {
         background: #1a2e1a;
         border-color: #4a7c59;
     }
 
-    .word-detail {
+    html:not([data-theme="light"]) .word-detail {
         background: #222;
         border-color: #444;
     }
 
-    .word-detail-original {
+    html:not([data-theme="light"]) .word-detail-original {
         color: #eee;
     }
 
-    .word-detail-value {
+    html:not([data-theme="light"]) .word-detail-value {
         color: #ddd;
     }
 
-    .word-detail-definition {
+    html:not([data-theme="light"]) .word-detail-definition {
         color: #bbb;
         border-top-color: #444;
     }
 
-    .word-detail-header {
+    html:not([data-theme="light"]) .word-detail-header {
         border-bottom-color: #444;
     }
 
-    .interlinear-heading {
+    html:not([data-theme="light"]) .interlinear-heading {
         color: #ddd;
         border-bottom-color: #444;
     }