On a computer, steer with the arrow keys or WASD: left and right turn, up and down pitch. Or click and hold anywhere and drag: a joystick appears under the pointer, and letting go flies straight. A resting pointer never steers. On a phone, tilt it: roll to turn, lean to pitch, and tap the screen to recentre. R or the Turn button flips you around, Shift or Stop brakes, B or Back reverses, and Space pauses. Change speed any time with + / − or the slider. The sub gently follows the vessel; steer into an opening to take a branch. Facing a wall stops you so you can turn away without a bump.