Complex sentence: Levels are divided into areas of light and darkness; the player character is invisible while in the latter, though he may be given away by any sounds he may make, such as by running, which are represented visually by a rapidly expanding circle.
Split into simpler sentences: Levels are divided into areas of light and darkness; the player character is invisible while in the latter. Sounds such as running may also give away the player character's location and are represented visually by a rapidly expanding circle.