System Menu

Sliders

Sound Effects Volume
Music Volume
Game Speed
Scroll Speed: This affects how quickly the game scrolls when you move the mouse to the edge of the screen or when you use the arrow keys.

Load/Save Game: This brings up a small dialog which displays all of your saved games. You can click on a save name to select it, or type a new name in the box at the top of the screen. (When typing text, press Enter to save your changes and exit edit mode, or Esc to cancel.)
Restate Objective: Shows a screen explaining what you should be doing, in case you forgot.
Start Again: Restarts the current mission from the beginning, discarding any progress you have made.
Abort: Exits the current mission.
Exit to System: Quits the game.