old_contents: const {app, BrowserWindow} = require('electron');
  
  let mainWindow;
  
  app.on('ready', () => {
    mainWindow = new BrowserWindow({
        height: 600,
        width: 800,
        frame: false,
        transparent: true
    });
  
    mainWindow.loadURL('http://localhost:9000');
  });
  
new_contents: const {app, BrowserWindow} = require('electron');
  
  let mainWindow;
  
  app.on('ready', () => {
    mainWindow = new BrowserWindow({
        height: 600,
        width: 900,
        frame: false,
        transparent: true
    });
  
    mainWindow.loadURL('http://localhost:9000');
  });
  
subject: change window with