Use the viewport command if you only want to see 400x300 on a 800x600 screen (why not use the full screen though?)
Secondly, store a value in two variables, which I usually call cornerx,cornery, which stores the world position of the upper left most pixel on the screen. Then simply subtract cornerx,cornery from the world coordinates of your object and they will now be positioned correctly on the screen.
Secondly, store a value in two variables, which I usually call cornerx,cornery, which stores the world position of the upper left most pixel on the screen. Then simply subtract cornerx,cornery from the world coordinates of your object and they will now be positioned correctly on the screen.