Handling multiple screen resolutions for made "Apps"

I'm working on an app in Max, but my problem currently is about how to handle multiple resolutions. For example, if a persons screen is larger than mine, if they drag out the corner to make the window larger, it just adds blank space. And if the screen is smaller, then things are cut-off and scrolling is required.

Is there a way to either scale everything to the resolution size, or use something similar to "float" in CSS/HTML where things will move dynamically? Or is there a better solution?