DHTML Demo by Alan Leish

(1) Line up your periscope vertically with the moving enemy submarine.
     (the target sub can only move right or left)

(2) Position your periscope ahead of the moving submarine

(3) Move the periscope headon toward the moving submarine.
     (When the submarine moves right, move the periscope left)
     (When the submarine moves left, move the periscope right)

(4) Move quickly since the key to sinking the sub is both speed and position.
     Move quickly enough so the cursor is slightly ahead of your periscope.
     Positioning the crosshair dead center won't work
     because your torpedo needs a bit of time to reach the target.

(5) Don't worry about clicking or double-clicking the mouse
     since your torpedo fires automatically when properly positioned.