I'm trying to modify a CSS statement for a body image graphic. Unfortunately, the CSS as shown doesn't adjust for device size. The current result is a great image for desktops, but horribly blown up for smaller devices.

#bodyimage { background-image:
url(%resource(image_2.jpg)%); }

How can I conditionally control the image by device size, or conditionally allow for two or three graphics based on device size?