diff --git a/main-electron.js b/main-electron.js
index 32f628da..7398cae6 100644
--- a/main-electron.js
+++ b/main-electron.js
@@ -9,166 +9,181 @@ const fs = require("fs");
 let win;
 
 function createWindow() {
-  // Create the browser window.
-  win = new BrowserWindow({
-    width: 377,
-    height: 800,
-    title: "Sengi",
-    backgroundColor: "#FFF",
-    useContentSize: true
-  });
+    // Create the browser window.
+    win = new BrowserWindow({
+        width: 377,
+        height: 800,
+        title: "Sengi",
+        backgroundColor: "#FFF",
+        useContentSize: true
+    });
 
-  var server = http.createServer(requestHandler).listen(9527);
-  win.loadURL("http://localhost:9527");
+    var server = http.createServer(requestHandler).listen(9527);
+    win.loadURL("http://localhost:9527");
 
-  const template = [
-    {
-      label: "View",
-      submenu: [
-        { role: "reload" },
-        { role: "forcereload" },
-        { type: "separator" },
-        { role: "close" },
-        { role: 'quit' }
-      ]
-    },
-    {
-      role: "help",
-      submenu: [
-        { role: "toggledevtools" },
+    const template = [
         {
-          label: "Open GitHub project",
-          click() {
-            require("electron").shell.openExternal(
-              "https://github.com/NicolasConstant/sengi"
-            );
-          }
+            label: "View",
+            submenu: [
+                { role: "reload" },
+                { role: "forcereload" },
+                { type: "separator" },
+                { role: "close" },
+                { role: 'quit' }
+            ]
+        },
+        {
+            role: "help",
+            submenu: [
+                { role: "toggledevtools" },
+                {
+                    label: "Open GitHub project",
+                    click() {
+                        require("electron").shell.openExternal(
+                            "https://github.com/NicolasConstant/sengi"
+                        );
+                    }
+                }
+            ]
         }
-      ]
+    ];
+
+    const menu = Menu.buildFromTemplate(template);
+    win.setMenu(menu);
+
+    // Check if we are on a MAC
+    if (process.platform === "darwin") {
+        // Create our menu entries so that we can use MAC shortcuts
+        Menu.setApplicationMenu(
+            Menu.buildFromTemplate([
+                {
+                    label: "Edit",
+                    submenu: [
+                        { role: "undo" },
+                        { role: "redo" },
+                        { type: "separator" },
+                        { role: "cut" },
+                        { role: "copy" },
+                        { role: "paste" },
+                        { role: "pasteandmatchstyle" },
+                        { role: "delete" },
+                        { role: "selectall" },
+                        { type: "separator" },
+                        { role: "close" },
+                        { role: 'quit' }
+                    ]
+                },
+                {
+                    label: "View",
+                    submenu: [{ role: "reload" }, { role: "forcereload" }]
+                },
+                {
+                    role: "help",
+                    submenu: [
+                        { role: "toggledevtools" },
+                        {
+                            label: "Open GitHub project",
+                            click() {
+                                require("electron").shell.openExternal(
+                                    "https://github.com/NicolasConstant/sengi"
+                                );
+                            }
+                        }
+                    ]
+                }
+            ])
+        );
     }
-  ];
 
-  const menu = Menu.buildFromTemplate(template);
-  win.setMenu(menu);
+    // Open the DevTools.
+    // win.webContents.openDevTools()
 
-  // Check if we are on a MAC
-  if (process.platform === "darwin") {
-    // Create our menu entries so that we can use MAC shortcuts
-    Menu.setApplicationMenu(
-      Menu.buildFromTemplate([
-        {
-          label: "Edit",
-          submenu: [
-            { role: "undo" },
-            { role: "redo" },
-            { type: "separator" },
-            { role: "cut" },
-            { role: "copy" },
-            { role: "paste" },
-            { role: "pasteandmatchstyle" },
-            { role: "delete" },
-            { role: "selectall" },
-            { type: "separator" },
-            { role: "close" },
-            { role: 'quit' }
-          ]
-        },
-        {
-          label: "View",
-          submenu: [{ role: "reload" }, { role: "forcereload" }]
-        },
-        {
-          role: "help",
-          submenu: [
-            { role: "toggledevtools" },
-            {
-              label: "Open GitHub project",
-              click() {
-                require("electron").shell.openExternal(
-                  "https://github.com/NicolasConstant/sengi"
-                );
-              }
-            }
-          ]
-        }
-      ])
-    );
-  }
+    //open external links to browser
+    win.webContents.on("new-window", function (event, url) {
+        event.preventDefault();
+        shell.openExternal(url);
+    });
 
-  // Open the DevTools.
-  // win.webContents.openDevTools()
-
-  //open external links to browser
-  win.webContents.on("new-window", function(event, url) {
-    event.preventDefault();
-    shell.openExternal(url);
-  });
-
-  // Emitted when the window is closed.
-  win.on("closed", () => {
-    // Dereference the window object, usually you would store windows
-    // in an array if your app supports multi windows, this is the time
-    // when you should delete the corresponding element.
-    win = null;
-  });
+    // Emitted when the window is closed.
+    win.on("closed", () => {
+        // Dereference the window object, usually you would store windows
+        // in an array if your app supports multi windows, this is the time
+        // when you should delete the corresponding element.
+        win = null;
+    });
 }
 
 function requestHandler(req, res) {
-  var file = req.url == "/" ? "/index.html" : req.url,
-    root = __dirname + "/dist",
-    page404 = root + "/404.html";
+    var file = req.url == "/" ? "/index.html" : req.url,
+        root = __dirname + "/dist",
+        page404 = root + "/404.html";
 
-  if (file.includes("register") || file.includes("home")) file = "/index.html";
+    if (file.includes("register") || file.includes("home")) file = "/index.html";
 
-  getFile(root + file, res, page404);
+    getFile(root + file, res, page404);
 }
 
 function getFile(filePath, res, page404) {
-  console.warn(`filePath: ${filePath}`);
-  fs.exists(filePath, function(exists) {
-    if (exists) {
-      fs.readFile(filePath, function(err, contents) {
-        if (!err) {
-          res.end(contents);
+    console.warn(`filePath: ${filePath}`);
+    fs.exists(filePath, function (exists) {
+        if (exists) {
+            fs.readFile(filePath, function (err, contents) {
+                if (!err) {
+                    res.end(contents);
+                } else {
+                    console.dir(err);
+                }
+            });
         } else {
-          console.dir(err);
+            fs.readFile(page404, function (err, contents) {
+                if (!err) {
+                    res.writeHead(404, { "Content-Type": "text/html" });
+                    res.end(contents);
+                } else {
+                    console.dir(err);
+                }
+            });
         }
-      });
-    } else {
-      fs.readFile(page404, function(err, contents) {
-        if (!err) {
-          res.writeHead(404, { "Content-Type": "text/html" });
-          res.end(contents);
-        } else {
-          console.dir(err);
-        }
-      });
-    }
-  });
+    });
 }
 
 app.commandLine.appendSwitch("force-color-profile", "srgb");
 
-// This method will be called when Electron has finished
-// initialization and is ready to create browser windows.
-// Some APIs can only be used after this event occurs.
-app.on("ready", createWindow);
+
+const gotTheLock = app.requestSingleInstanceLock();
+
+if (!gotTheLock) {
+    app.quit();
+} else {
+    app.on('second-instance', (event, commandLine, workingDirectory) => {
+        // Someone tried to run a second instance, we should focus our window.
+        if (win) {
+            if (win.isMinimized()) win.restore()
+            win.focus()
+        }
+    });
+
+    // This method will be called when Electron has finished
+    // initialization and is ready to create browser windows.
+    // Some APIs can only be used after this event occurs.
+    app.on("ready", createWindow);
+}
 
 // Quit when all windows are closed.
 app.on("window-all-closed", () => {
-  // On macOS it is common for applications and their menu bar
-  // to stay active until the user quits explicitly with Cmd + Q
-  if (process.platform !== "darwin") {
-    app.quit();
-  }
+    // On macOS it is common for applications and their menu bar
+    // to stay active until the user quits explicitly with Cmd + Q
+    if (process.platform !== "darwin") {
+        app.quit();
+    }
 });
 
 app.on("activate", () => {
-  // On macOS it's common to re-create a window in the app when the
-  // dock icon is clicked and there are no other windows open.
-  if (win === null) {
-    createWindow();
-  }
+    // On macOS it's common to re-create a window in the app when the
+    // dock icon is clicked and there are no other windows open.
+    if (win === null) {
+        createWindow();
+    }
 });
 
 // In this file you can include the rest of your app's specific main process