Step 1

Your project starts with a basic HTML container and some corresponding CSS. Your first task will be to programmatically generate the cells for your spreadsheet. The global `window` object represents the browser window (or tab). It has an `onload` property which allows you to define behavior when the window has loaded the entire page, including stylesheets and scripts. Start by setting the `onload` property of `window` to an arrow function with no parameters. In the function, declare a `container` variable and assign it the value of getting the element by the `id` of `"container"`.