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To unlock all available missions, create a new profile called "AccessAllAreas". Once you complete the game, it becomes a loadable profile without the need to type it in manually.

After completing the game, you can access the map editor from the area selection screen. To enable the map editor before then, open "preferences.txt" within your saved game folder (located within your User folder), and add ModSystemEnabled = 1 to the end of the file.