diff --git a/AdaptiveBrightness/main_window.cpp b/AdaptiveBrightness/main_window.cpp
index e28f32c..b1fb0a9 100644
--- a/AdaptiveBrightness/main_window.cpp
+++ b/AdaptiveBrightness/main_window.cpp
@@ -1,5 +1,10 @@
 #include "main_window.hpp"
 
+#include <algorithm>
+#include <numeric>
+
+#include <cmath>
+
 #include <QtDebug>
 #include <QtGlobal>
 
@@ -100,4 +105,66 @@ void MainWindow::loadIcons()
 void MainWindow::updateState()
 {
     qDebug(ltr("Updating state"));
+
+    bool sensorError = false;
+    bool monitorError = false;
+    size_t iconBrightness = 0;
+
+    const auto getAverageSensorValue = [this](float& brightness) {
+        if(m_sensors.empty()) {
+            return false;
+        }
+
+        std::vector<float> values;
+
+        for(auto& sensor: m_sensors) {
+            const auto sensorValues = sensor.readValues();
+            if(!sensor) {
+                return false;
+            }
+            values.insert(values.end(), sensorValues.begin(), sensorValues.end());
+        }
+
+        brightness = std::accumulate(values.begin(), values.end(), 0.f) / values.size();
+        return true;
+    };
+
+    const auto setAllMonitorsBrightness = [this](float& brightness) {
+        if(m_monitors.empty()) {
+            return false;
+        }
+
+        bool errorOccurred = false;
+        for(auto& monitor: m_monitors) {
+            if(!monitor.setBrightness(brightness)) {
+                errorOccurred = true;
+            }
+        }
+        return !errorOccurred;
+    };
+
+    if(!getAverageSensorValue(m_brightness)) {
+        m_sensors = enumerateSensors();
+        qInfo(ltr("At least one sensor became invalid, re-enumerating sensors found %1 valid sensor(s)").arg(m_sensors.size()));
+        sensorError = true;
+    }
+
+    const auto roundedBrightness = std::round(utils::map(m_brightness, 0.f, 1.f, 0, 8));
+    iconBrightness = std::clamp<size_t>(roundedBrightness, 0, 8);
+
+    if(!setAllMonitorsBrightness(m_brightness)) {
+        m_monitors = enumerateMonitors();
+        qInfo(ltr("At least one monitor became invalid, re-enumerating monitors found %1 valid monitor(s)").arg(m_monitors.size()));
+        monitorError = true;
+    }
+
+    if(!sensorError && !monitorError && m_trayIcon) {
+        m_trayIcon->setIcon(*m_sensorStateIcons[iconBrightness]);
+    }
+    else if(sensorError && !monitorError && m_trayIcon) {
+        m_trayIcon->setIcon(*m_noSensorStateIcons[iconBrightness]);
+    }
+    else if(m_trayIcon) {
+        m_trayIcon->setIcon(*m_errorIcon);
+    }
 }
diff --git a/AdaptiveBrightness/main_window.hpp b/AdaptiveBrightness/main_window.hpp
index 12f9f07..5dc4c4c 100644
--- a/AdaptiveBrightness/main_window.hpp
+++ b/AdaptiveBrightness/main_window.hpp
@@ -2,6 +2,7 @@
 
 #include <array>
 #include <memory>
+#include <vector>
 
 #include <QAction>
 #include <QIcon>
@@ -40,7 +41,7 @@ class MainWindow : public QMainWindow {
 
     QTimer* m_timer = nullptr;
 
-    float m_brightness;
+    float m_brightness = 0.5f;
 
     std::vector<Sensor> m_sensors;
     std::vector<Monitor> m_monitors;