diff --git a/index.html b/index.html
index 1d86d29..ee764ec 100644
--- a/index.html
+++ b/index.html
@@ -10,7 +10,7 @@
   <link rel="manifest" href="manifest.json">
   <link rel="icon" type="image/svg+xml" href="icon.svg">
   <link rel="apple-touch-icon" href="icon-192.png">
-  <link rel="stylesheet" href="styles.css?v=14">
+  <link rel="stylesheet" href="styles.css?v=15">
 </head>
 <body>
   <div id="app">
@@ -158,10 +158,10 @@
 
   </div>
 
-  <script type="module" src="app.js?v=14"></script>
+  <script type="module" src="app.js?v=15"></script>
   <script>
     if ('serviceWorker' in navigator) {
-      navigator.serviceWorker.register('/sw.js?v=14').catch(() => {});
+      navigator.serviceWorker.register('/sw.js?v=15').catch(() => {});
     }
   </script>
 </body>
diff --git a/styles.css b/styles.css
index c387d98..e03791a 100644
--- a/styles.css
+++ b/styles.css
@@ -15,6 +15,7 @@
   --text-dim: #a0a0b0;
   --correct: #2ecc71;
   --incorrect: #e74c3c;
+  --border: rgba(255,255,255,0.08);
   --border-radius: 12px;
   --safe-top: env(safe-area-inset-top);
   --safe-bottom: env(safe-area-inset-bottom);
@@ -32,6 +33,7 @@
     --text-dim: #555566;
     --correct: #27ae60;
     --incorrect: #c0392b;
+    --border: #d0d0d0;
   }
 }
 
@@ -114,7 +116,7 @@ body {
 .lang-select {
   background: var(--bg-light);
   color: var(--text);
-  border: 2px solid transparent;
+  border: 2px solid var(--border);
   border-radius: 8px;
   padding: 10px 16px;
   font-size: 0.95rem;
@@ -164,6 +166,7 @@ body {
 .btn-secondary {
   background: var(--bg-card);
   color: var(--text);
+  border: 1px solid var(--border);
 }
 
 .btn-large {
@@ -219,7 +222,7 @@ body {
 .option-btn {
   padding: 14px 12px;
   background: var(--bg-light);
-  border: 2px solid transparent;
+  border: 2px solid var(--border);
   border-radius: 8px;
   color: var(--text);
   font-size: 0.95rem;
@@ -263,6 +266,7 @@ body {
   align-items: center;
   padding: 16px 20px;
   background: var(--bg-light);
+  border-bottom: 1px solid var(--border);
   flex-shrink: 0;
   position: relative;
 }
@@ -425,7 +429,7 @@ body {
 .choice-btn {
   padding: 18px 20px;
   background: var(--bg-card);
-  border: 2px solid transparent;
+  border: 2px solid var(--border);
   border-radius: var(--border-radius);
   color: var(--text);
   font-size: 1.3rem;
@@ -486,7 +490,7 @@ body {
 .numpad-key {
   padding: 18px;
   background: var(--bg-light);
-  border: none;
+  border: 1px solid var(--border);
   border-radius: 8px;
   color: var(--text);
   font-size: 1.4rem;
@@ -581,6 +585,7 @@ body {
   padding: 14px 16px;
   background: var(--bg-light);
   border-radius: 8px;
+  border: 1px solid var(--border);
   border-left: 4px solid var(--incorrect);
 }
 
diff --git a/sw.js b/sw.js
index 157d4f0..f296d39 100644
--- a/sw.js
+++ b/sw.js
@@ -1,4 +1,4 @@
-const CACHE_NAME = 'numnum-v14';
+const CACHE_NAME = 'numnum-v15';
 const ASSETS = [
   '/',
   '/index.html',
