User of widescreen monitors see a distorted game if the programmer did not offers a necessary resolution.

If you want to offer at least the right aspects for all types of monitors you can use the following code to set the right camera aspect.

Code:
var gv_scr_width;
var gv_scr_height;

//...

// before resolution change
gv_scr_width=sys_metrics(0);
gv_scr_height=sys_metrics(1);	

// set the resolution here
// ...
	
// set aspect
camera.aspect=(screen_size.y/screen_size.x)/(gv_scr_height/gv_scr_width);