diff --git a/network-poc/frontend/src/pages/index.astro b/network-poc/frontend/src/pages/index.astro
index ae58242..2e35465 100644
--- a/network-poc/frontend/src/pages/index.astro
+++ b/network-poc/frontend/src/pages/index.astro
@@ -29,6 +29,10 @@ import Settings from "../components/Settings.astro";
                 <h1 style="margin-bottom:0"><span style="color:#ff6b00">Kipinä</span> Agentic Playground</h1>
                 <p style="color:#8b949e;margin:0">AI-ohjelmistokehitystiimi · <span id="hub-version">-</span></p>
             </div>
+            <div style="display:flex;gap:4px;align-items:center">
+                <button onclick="changeFontSize(-1)" class="btn btn-muted" style="font-size:14px;padding:2px 8px" title="Pienennä fonttia">A-</button>
+                <button onclick="changeFontSize(1)" class="btn btn-muted" style="font-size:14px;padding:2px 8px" title="Suurenna fonttia">A+</button>
+            </div>
         </div>
 
         <!-- Välilehdet -->
@@ -53,6 +57,17 @@ import Settings from "../components/Settings.astro";
 
     <script is:inline>
     // === Helpers ===
+    // Fonttikoon säätö (±20%, 5 askelta)
+    let fontScale = parseFloat(localStorage.getItem('kpn-font-scale') || '1');
+    document.documentElement.style.fontSize = (fontScale * 16) + 'px';
+
+    window.changeFontSize = function(dir) {
+        fontScale = Math.max(0.8, Math.min(1.2, fontScale + dir * 0.05));
+        fontScale = Math.round(fontScale * 100) / 100;
+        document.documentElement.style.fontSize = (fontScale * 16) + 'px';
+        localStorage.setItem('kpn-font-scale', String(fontScale));
+    };
+
     function esc(str) {
         if (!str) return '';
         return String(str).replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;').replace(/"/g,'&quot;');
diff --git a/network-poc/frontend/src/styles/global.css b/network-poc/frontend/src/styles/global.css
index 7a08eb3..71731f1 100644
--- a/network-poc/frontend/src/styles/global.css
+++ b/network-poc/frontend/src/styles/global.css
@@ -14,7 +14,7 @@
 
 body {
     font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
-    font-size: 16px;
+    font-size: 1rem;
     background: var(--bg);
     color: var(--text);
     min-height: 100vh;