using ctrl on the opposite side of the keyboard from wasd ( which is the natural hand placement ) on my keyboard shuts the game down ... a better choice of keys would be arrows for movement , z x or space for fire .
if you really want to use wasd for movement then use something that doesnt have a dual function for fire - e.g the space bar - and is far enough away from the movement keys so you can use both hands .
i must have had to comment on at least 7 games recently with strange controls , seems to be a theme !