Yeh, I didn't even have to use much code! The below is all I used (it's in GML, the in-built language):
Create Event
width = display_get_width()
height = display_get_height()
Step Event
window_set_position(random(width),random(height))
wind_width = window_get_width()
wind_height = window_get_height()
window_set_size(wind_width -5, wind_height-3)