2.5D weapon aiming with cross hairs help needed

Hi, I am trying to create a 2.5D platformer game with controls similar to Worms where the keys W,S aims the cursor up and down. So far, I managed to create the game character to shoot, but it shoots in a fixed angle without any cross hairs. Any idea how can I modify my weapons to shoot in a direction decided by the position of a cross hair?

You can use the lookat function on the gun and then feed it the mouse position data.

You may need the screen point to ray function to get a point in 3D space to aim at or you can work out the angle from the mouse position yourself.