diff --git a/README-STEAM.md b/README-STEAM.md
index bc3bd7c..f06f964 100644
--- a/README-STEAM.md
+++ b/README-STEAM.md
@@ -135,22 +135,68 @@ gamepadAPI.setDebug(true);
 
 If Steam is still applying mouse emulation:
 
-1. **Verify gamepad polling is active**: Open DevTools (F12) and run `gamepadAPI.getState()` - check that `isPolling` is `true`
-2. **Check gamepad connection**: Run `gamepadAPI.getConnected()` to see detected gamepads
-3. **Press a button first**: On Linux, the `gamepadconnected` event may not fire until the first button press
-4. **Enable debug mode**: Run `gamepadAPI.setDebug(true)` to see detailed logs
-5. **Restart the app**: Close Nebula completely and relaunch from Steam
+1. **Configure Steam Input per-game** (most reliable fix):
+   - In Steam, right-click Nebula → Properties → Controller
+   - Set **"Override for Nebula"** to **"Disable Steam Input"**
+   - This completely disables Steam's input emulation for this app
+
+2. **Verify gamepad polling is active**: Open DevTools (F12) and run `gamepadAPI.getState()` - check that `isPolling` is `true`
+3. **Check gamepad connection**: Run `gamepadAPI.getConnected()` to see detected gamepads
+4. **Press a button first**: On Linux, the `gamepadconnected` event may not fire until the first button press
+5. **Enable debug mode**: Run `gamepadAPI.setDebug(true)` to see detailed logs
+6. **Restart the app**: Close Nebula completely and relaunch from Steam
 
 ### Steam Launch Options
 
+Add these to your Steam launch options (Right-click game → Properties → Launch Options):
+
+```bash
+# Disable Steam Input completely (recommended for native controller support)
+SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 %command%
+
+# Force native gamepad without Steam's emulation layer
+STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD=0 %command%
+
+# Combined - full native controller mode with Big Picture UI
+SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD=0 %command% --big-picture
+
+# If you need to debug controller issues
+SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 %command% --big-picture 2>&1 | tee ~/nebula-debug.log
 ```
-# Force Big Picture Mode
+
+### Steam Deck Recommended Setup
+
+For the best experience on Steam Deck:
+
+1. **Add Nebula as a Non-Steam Game** (if not using Steamworks version)
+2. **Controller Settings**:
+   - Right-click Nebula → Properties → Controller
+   - Set to **"Disable Steam Input"** 
+3. **Launch Options**:
+   ```
+   SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD=0 %command% --big-picture
+   ```
+4. **Shortcuts** (optional):
+   - Configure gamepad shortcuts in Steam for Steam button actions (screenshots, etc.)
+
+### Why This Is Needed
+
+Steam Deck / SteamOS Game Mode applies "Desktop Configuration" mouse/keyboard emulation to apps that don't appear to handle controller input. Even though Nebula polls `navigator.getGamepads()` continuously, Steam's input layer initializes before the app can signal its intent.
+
+The solution is two-fold:
+1. **Environment variables** (`SDL_GAMECONTROLLER_*`) signal to Steam's SDL-based input layer early
+2. **Steam Input settings** ("Disable Steam Input") bypasses the emulation entirely
+
+### Force Big Picture Mode
+
+```bash
+# Via command line
 ./Nebula --big-picture
 
+# Via environment
+NEBULA_BIG_PICTURE=1 ./Nebula
+
 # Disable Big Picture Mode  
 ./Nebula --no-big-picture
-
-# Environment variables also work
-NEBULA_BIG_PICTURE=1 ./Nebula
 NEBULA_NO_BIG_PICTURE=1 ./Nebula
 ```
diff --git a/documentation/BIG_PICTURE_MODE.md b/documentation/BIG_PICTURE_MODE.md
index f84e4bd..6791cc0 100644
--- a/documentation/BIG_PICTURE_MODE.md
+++ b/documentation/BIG_PICTURE_MODE.md
@@ -2,6 +2,36 @@
 
 Nebula Browser includes a **Big Picture Mode** - a controller-friendly, console-style interface designed for Steam Deck, handheld devices, and living room setups.
 
+## ⚠️ Steam Deck: Disabling Mouse Emulation
+
+If Steam is emulating mouse/keyboard input with the joysticks (overriding native controller support), you need to configure Steam Input:
+
+### Quick Fix - Steam Launch Options
+
+Add this to your Steam launch options (Right-click → Properties → Launch Options):
+
+```bash
+SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD=0 %command% --big-picture
+```
+
+### Recommended Fix - Disable Steam Input Per-Game
+
+1. In Steam, right-click **Nebula** → **Properties** → **Controller**
+2. Set **"Override for Nebula"** to **"Disable Steam Input"**
+3. This completely disables Steam's input emulation for this app
+
+### Using the Steam Deck Launcher Script
+
+For the easiest setup, use the included launcher script:
+
+1. Set Steam launch options to: `./start-steamdeck.sh`
+
+The script automatically sets all necessary environment variables.
+
+See [README-STEAM.md](../README-STEAM.md) for detailed troubleshooting.
+
+---
+
 ## Features
 
 ### 🎮 Controller Support
diff --git a/main.js b/main.js
index 0e7c338..6041dea 100644
--- a/main.js
+++ b/main.js
@@ -1,3 +1,38 @@
+// =============================================================================
+// STEAM DECK / STEAMOS CONTROLLER INPUT FIX
+// =============================================================================
+// These environment variables MUST be set before Electron/Chromium initializes.
+// They signal to Steam's input layer that this application handles its own
+// controller input and should NOT have mouse/keyboard emulation applied.
+//
+// Without these, Steam assumes the app needs Desktop mouse emulation when running
+// in Game Mode, which overrides the app's native gamepad support.
+// =============================================================================
+
+// Tell SDL (and by extension Steam Input) that this app uses the gamepad API
+// SDL_GAMECONTROLLERCONFIG is used by SDL to know about controllers
+process.env.SDL_GAMECONTROLLERCONFIG = process.env.SDL_GAMECONTROLLERCONFIG || '';
+
+// Signal that this app handles gamepad input natively
+// This prevents Steam from applying mouse emulation in Game Mode
+process.env.SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD = '1';
+
+// Prevent Steam from remapping the controller to keyboard/mouse
+// Setting to '1' tells Steam we want raw controller access
+process.env.SDL_GAMECONTROLLER_IGNORE_DEVICES = '';
+
+// Disable Steam's overlay input hooks for this process if possible
+process.env.SteamNoOverlayUIDrawing = process.env.SteamNoOverlayUIDrawing || '0';
+
+// Tell Steam Input we're a native controller app
+// When STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD is 0, Steam won't virtualize the gamepad
+if (!process.env.STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD) {
+  process.env.STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD = '0';
+}
+
+// Hint that this is a game/controller-focused app
+process.env.SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS = '1';
+
 const { app, BrowserWindow, ipcMain, session, screen, shell, dialog, Menu, clipboard, webContents } = require('electron');
 const { autoUpdater } = require('electron-updater');
 const { pathToFileURL } = require('url');
@@ -61,6 +96,30 @@ try {
   // Non-fatal: some environments may not allow commandLine changes at this time.
 }
 
+// =============================================================================
+// GAMEPAD / CONTROLLER CHROMIUM FLAGS
+// =============================================================================
+// Enable native gamepad support in Chromium - helps with Steam Deck compatibility
+try {
+  // Enable raw gamepad access (bypasses Steam's virtualization when possible)
+  app.commandLine.appendSwitch('enable-gamepad-extensions');
+  
+  // Ensure the Gamepad API is enabled and working
+  app.commandLine.appendSwitch('enable-blink-features', 'GamepadExtensions');
+  
+  // On Linux/Steam Deck, this can help with gamepad detection
+  if (process.platform === 'linux') {
+    // Disable Chromium's sandbox for gamepad access if having issues
+    // (Only needed in some SteamOS configurations)
+    // app.commandLine.appendSwitch('no-sandbox');
+    
+    // Use the system's gamepad config rather than Chromium's built-in
+    app.commandLine.appendSwitch('enable-features', 'WebGamepad');
+  }
+} catch (e) {
+  console.warn('[Gamepad] Failed to set Chromium gamepad flags:', e.message);
+}
+
 // Configure GPU settings before app is ready
 gpuConfig.configure();
 
diff --git a/preload.js b/preload.js
index ca40fdd..b072151 100644
--- a/preload.js
+++ b/preload.js
@@ -224,6 +224,29 @@ window.addEventListener('beforeunload', () => {
   }
 });
 
+// =============================================================================
+// EARLY GAMEPAD INITIALIZATION - Critical for Steam Deck
+// =============================================================================
+// Initialize gamepad polling as EARLY as possible to signal Steam Input
+// that this app handles controller input natively. This MUST happen before
+// Steam decides to apply mouse/keyboard emulation.
+// 
+// We try to initialize immediately when preload runs, not waiting for DOMContentLoaded,
+// because Steam's input layer makes decisions very early in the process lifecycle.
+// =============================================================================
+
+// Try immediate initialization (works in most Electron contexts)
+try {
+  if (typeof navigator !== 'undefined' && navigator.getGamepads) {
+    // Start polling immediately - this is the key signal to Steam
+    initGamepadHandler();
+    console.log('[NebulaGamepad] Early initialization successful - Steam should recognize controller input');
+  }
+} catch (e) {
+  // Will retry on DOMContentLoaded
+  console.log('[NebulaGamepad] Early init deferred, will retry on DOM ready');
+}
+
 // =============================================================================
 // DOM READY & INITIALIZATION
 // =============================================================================
@@ -234,8 +257,10 @@ window.addEventListener('DOMContentLoaded', () => {
   domReady = true;
   console.log("Browser UI loaded.");
   
-  // Initialize gamepad handler for Steam Deck/SteamOS support
-  initGamepadHandler();
+  // Re-initialize gamepad handler if early init failed
+  if (!gamepadState.initialized) {
+    initGamepadHandler();
+  }
 });
 
 // Optimized API exposure with error handling and caching
diff --git a/start-steamdeck.sh b/start-steamdeck.sh
new file mode 100644
index 0000000..3a9aa26
--- /dev/null
+++ b/start-steamdeck.sh
@@ -0,0 +1,66 @@
+#!/bin/bash
+# =============================================================================
+# NEBULA BROWSER - Steam Deck / SteamOS Launch Script
+# =============================================================================
+# This script is designed for launching Nebula on Steam Deck in Game Mode.
+# It sets necessary environment variables to disable Steam's mouse/keyboard
+# emulation so the app's native controller support works properly.
+#
+# Usage:
+#   1. Add Nebula as a Non-Steam game (or via Steamworks)
+#   2. Set launch options to: ./start-steamdeck.sh
+#   OR
+#   3. Use this script's environment variables in Steam Launch Options:
+#      SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0 %command% --big-picture
+# =============================================================================
+
+cd "$(dirname "$0")"
+
+# =============================================================================
+# STEAM INPUT CONFIGURATION
+# =============================================================================
+# These variables tell Steam's input layer that this app handles controller
+# input natively and should NOT have mouse/keyboard emulation applied.
+
+# Disable Steam's virtual gamepad layer
+export SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD=0
+export STEAM_INPUT_ENABLE_VIRTUAL_GAMEPAD=0
+
+# Allow raw gamepad access
+export SDL_GAMECONTROLLER_IGNORE_DEVICES=""
+
+# Allow background gamepad events (useful when app doesn't have focus)
+export SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS=1
+
+# Hint to SDL that we're using gamepads natively
+export SDL_GAMECONTROLLERCONFIG="${SDL_GAMECONTROLLERCONFIG:-}"
+
+# =============================================================================
+# NEBULA CONFIGURATION
+# =============================================================================
+
+# Enable Big Picture Mode for controller-friendly UI
+export NEBULA_BIG_PICTURE=1
+
+# Enable GPU acceleration on Linux
+export NEBULA_GPU_ALLOW_LINUX=1
+
+# =============================================================================
+# LAUNCH
+# =============================================================================
+
+# Check if we're in an AppImage/AppDir or dev environment
+if [ -f "./nebula" ]; then
+    # Packaged AppDir
+    exec ./nebula --big-picture "$@"
+elif [ -f "./Nebula" ]; then
+    # Alternate launcher name
+    exec ./Nebula --big-picture "$@"
+elif command -v npm &> /dev/null && [ -f "package.json" ]; then
+    # Development environment
+    npm start -- --big-picture "$@"
+else
+    echo "Error: Could not find Nebula executable or npm"
+    echo "Make sure you're running this script from the Nebula directory"
+    exit 1
+fi