you can use the layout grid + bootstrap classes to create responsive behavior.
See also: https://docs.mendix.com/refguide/layout-grid
Are you aware of which device is used for your tool? Because you could restrict the app to a maximum of X pixels width (I believe iPads have 768*1024 in portrait mode). So you could make an @media query in which your highest-level DIV element has a display:none at 768 or below pixels. See https://www.w3schools.com/cssref/css3_pr_mediaquery.asp for more info on how to use this.