diff --git a/server/app.py b/server/app.py
index c968e2f..9f93e9c 100644
--- a/server/app.py
+++ b/server/app.py
@@ -168,8 +168,12 @@ def create_app():
         if type_:
             query = query.filter(SensorReadout.type == type_)
         rows = query.order_by(SensorReadout.timestamp).all()
-        # Zakresy today i 24h: wszystkie pomiary jako punkty, bez uśredniania.
-        if range_ in ("today", "24h"):
+        # Zakresy today i 24h domyślnie zwracają wszystkie pomiary bez
+        # uśredniania; checkbox "hourly average" wymusza średnie godzinowe.
+        averaged = range_ not in ("today", "24h") or request.args.get(
+            "avg", "0"
+        ).lower() in ("1", "true", "yes")
+        if not averaged:
             return jsonify(
                 [
                     {
diff --git a/server/static/retro.css b/server/static/retro.css
index 49b1889..71b672e 100644
--- a/server/static/retro.css
+++ b/server/static/retro.css
@@ -63,6 +63,27 @@ h1 {
 
 h2 { color: var(--mc-bright); letter-spacing: 2px; }
 
+/* Yggdrasil logo — pixel art, so keep it crisp when scaled down.
+ * On the home page it spans the full width of the blue band. */
+.logo {
+    display: block;
+    width: 100%;
+    height: auto;
+    margin: 1rem auto;
+    image-rendering: pixelated;
+    border: 3px double var(--mc-bright);
+    box-shadow: 8px 8px 0 rgba(0, 0, 0, 0.45);
+}
+
+/* Small logo pinned to the right side of the black navbar. */
+nav { display: flex; align-items: center; }
+.nav-logo {
+    height: 68px;
+    width: auto;
+    margin-left: auto;
+    image-rendering: pixelated;
+}
+
 @keyframes mcblink { 50% { opacity: 0; } }
 
 /* --- Menu bar (navigation) --- */
@@ -166,6 +187,12 @@ button:disabled { opacity: 0.5; cursor: default; }
 
 #refresh-button { margin-top: 0.6rem; }
 
+/* Sensors page: the "hourly average" checkbox must stay a small inline
+ * box next to its text — the global `input { width: 100% }` would
+ * otherwise stretch it full-width and break the row layout. */
+#avg-label { display: flex; align-items: center; gap: 0.5em; margin-top: 0.6rem; }
+#avg-label input { width: auto; margin: 0; }
+
 .error {
     background: var(--mc-red);
     color: var(--mc-bright);
diff --git a/server/static/yggdrasil-logo.png b/server/static/yggdrasil-logo.png
new file mode 100644
index 0000000..3b5be7f
Binary files /dev/null and b/server/static/yggdrasil-logo.png differ
diff --git a/server/templates/docs.html b/server/templates/docs.html
index e91883b..cbd0d09 100644
--- a/server/templates/docs.html
+++ b/server/templates/docs.html
@@ -13,6 +13,7 @@
         <a href="{{ url_for('home') }}">Home</a>
         <a href="{{ url_for('sensors_page') }}">Sensors</a>
         <a href="{{ url_for('logout') }}">Log out</a>
+        <img class="nav-logo" src="{{ url_for('static', filename='yggdrasil-logo.png') }}" alt="Yggdrasil logo">
     </nav>
     <h1>Sensor Readouts &mdash; API Documentation</h1>
 
diff --git a/server/templates/home.html b/server/templates/home.html
index abf544b..4558f39 100644
--- a/server/templates/home.html
+++ b/server/templates/home.html
@@ -14,6 +14,7 @@
         <a href="{{ url_for('sensors_page') }}">Sensors</a>
         <a href="{{ url_for('api_docs') }}">API</a>
         <a href="{{ url_for('logout') }}">Log out</a>
+        <img class="nav-logo" src="{{ url_for('static', filename='yggdrasil-logo.png') }}" alt="Yggdrasil logo">
     </nav>
     <h1>Yggdrasil</h1>
     <div class="panel">
@@ -26,6 +27,7 @@
         </ul>
         <p class="hint">Tip: press <b>1</b>, <b>2</b> or <b>0</b> to navigate.</p>
     </div>
+    <img class="logo" src="{{ url_for('static', filename='yggdrasil-logo.png') }}" alt="Yggdrasil logo">
     <footer class="statusbar">
         <span>{{ user.username }}@yggdrasil:~$</span>
     </footer>
diff --git a/server/templates/sensors.html b/server/templates/sensors.html
index 0271a96..f0c0435 100644
--- a/server/templates/sensors.html
+++ b/server/templates/sensors.html
@@ -14,6 +14,7 @@
         <a href="{{ url_for('home') }}">Home</a>
         <a href="{{ url_for('api_docs') }}">API</a>
         <a href="{{ url_for('logout') }}">Log out</a>
+        <img class="nav-logo" src="{{ url_for('static', filename='yggdrasil-logo.png') }}" alt="Yggdrasil logo">
     </nav>
     <h1>Sensor Readouts</h1>
 
@@ -40,6 +41,9 @@
             <option value="month">Month</option>
             <option value="all" selected>All</option>
         </select>
+        <label id="avg-label" class="hidden">
+            <input type="checkbox" id="avg-checkbox"> hourly average
+        </label>
         <button id="refresh-button" type="button">[ Refresh ]</button>
     </div>
 
@@ -77,6 +81,8 @@
         const readoutsSection = document.getElementById('readouts-section');
         const readoutsBody = document.getElementById('readouts-body');
         const chartInfo = document.getElementById('chart-info');
+        const avgCheckbox = document.getElementById('avg-checkbox');
+        const avgLabel = document.getElementById('avg-label');
         let chart = null;
 
         // Strefa czasowa przeglądarki — backend liczy "today" od północy
@@ -97,20 +103,35 @@
             return d.toLocaleString('pl-PL', { timeZone: userTz });
         }
 
-        function formatChartLabel(iso) {
+        function formatChartLabel(iso, timeOnly) {
             const d = new Date(iso + 'Z');
-            return d.toLocaleString('pl-PL', { timeZone: userTz, hour: '2-digit', minute: '2-digit', day: '2-digit', month: '2-digit', year: 'numeric' });
+            if (timeOnly) {
+                return d.toLocaleString('pl-PL', { timeZone: userTz, hour: '2-digit', minute: '2-digit' });
+            }
+            return d.toLocaleString('pl-PL', { timeZone: userTz, day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit' });
         }
 
-        function chartInfoText(range) {
-            if (range === 'today') return `Raw measurements since local midnight (${userTz}) — no averaging.`;
-            if (range === '24h') return 'Raw measurements from the last 24 hours — no averaging.';
-            const period = range === 'week' ? 'the last 7 days'
+        function chartInfoText(range, averaged) {
+            if (!averaged) {
+                if (range === 'today') return `Raw measurements since local midnight (${userTz}) — no averaging.`;
+                return 'Raw measurements from the last 24 hours — no averaging.';
+            }
+            const period = range === 'today' ? 'today (since local midnight)'
+                : range === '24h' ? 'the last 24 hours'
+                : range === 'week' ? 'the last 7 days'
                 : range === 'month' ? 'the last 30 days'
                 : 'all stored data';
             return `Hourly averages over ${period} — each point is the mean of all measurements in that local hour (${userTz}).`;
         }
 
+        function isRawRange(range) {
+            return range === 'today' || range === '24h';
+        }
+
+        function updateAvgVisibility() {
+            avgLabel.classList.toggle('hidden', !isRawRange(rangeSelect.value));
+        }
+
         // Ciśnienie jest składowane w bazie w paskalach (tak wysyła firmware),
         // a wyświetlane w hektopaskalach z jednym miejscem po przecinku.
         function displayValue(type, value) {
@@ -176,14 +197,16 @@
 
             try {
                 // fetch hourly data for chart
-                const hourly = await fetchJSON(`/api/sensors/${sensorId}/readouts/hourly?type=${encodeURIComponent(type)}&range=${encodeURIComponent(range)}&tz=${encodeURIComponent(userTz)}`);
+                const averaged = !isRawRange(range) || avgCheckbox.checked;
+                const hourly = await fetchJSON(`/api/sensors/${sensorId}/readouts/hourly?type=${encodeURIComponent(type)}&range=${encodeURIComponent(range)}&tz=${encodeURIComponent(userTz)}&avg=${averaged ? '1' : '0'}`);
                 if (!hourly.length) throw new Error('no data for this range');
 
-                const labels = hourly.map(r => formatChartLabel(r.timestamp));
+                // Surowe punkty today/24h (~1/min) — mniejsze markery,
+                // żeby wykres był czytelny. W obrębie doby na osi X
+                // wystarczy sama godzina (też po uśrednieniu).
+                const dense = !averaged;
+                const labels = hourly.map(r => formatChartLabel(r.timestamp, isRawRange(range)));
                 const values = hourly.map(r => displayValue(type, r.value));
-                // Przy zakresach today/24h punktów jest dużo (~1/min),
-                // więc mniejsze markery żeby wykres był czytelny.
-                const dense = range === 'today' || range === '24h';
 
                 if (chart) chart.destroy();
                 const ctx = document.getElementById('chart').getContext('2d');
@@ -216,7 +239,7 @@
                 // The chart was created while the container was hidden,
                 // so force a re-measure now that it is visible.
                 chart.resize();
-                chartInfo.textContent = '> ' + chartInfoText(range);
+                chartInfo.textContent = '> ' + chartInfoText(range, averaged);
             } catch (err) {
                 chartError.textContent = '! Chart error: ' + err.message;
                 chartError.classList.remove('hidden');
@@ -265,8 +288,14 @@
             }
         });
 
-        rangeSelect.addEventListener('change', loadChart);
+        rangeSelect.addEventListener('change', () => {
+            updateAvgVisibility();
+            loadChart();
+        });
 
+        avgCheckbox.addEventListener('change', loadChart);
+
+        updateAvgVisibility();
         loadSensors();
     </script>
 </body>