memory and processor usage wise, best solution is to setup an array, say one third the resolution of the actualy graphics (you don't need pixel perfect collision really). So you've got an array now of say 400x400 (giving you a level size of 1200x1200), now check the coords of on screen objects, such as players and computer characters against coords in this array, as if it were a background.
Sorry I couldn't make it more simple, I'm very tired and need to sleep...... if you want some sample code, send me a mail.
Sorry I couldn't make it more simple, I'm very tired and need to sleep...... if you want some sample code, send me a mail.