StarCraft utilizes the elements of both higher ground and cover to add a deeper level of strategy to the game.
Experimenting with different units in these terrain types can yield some very effective tactics.
Units that are in trees are considered to be "in cover". Any units that are in cover only have a 70% chance of
being hit. Keeping more vulnerable units, such as Marines, under the cover of trees greatly increases their life
expectancy and allows them to hold their own against more powerful units.
Units attacking from lower ground to higher ground only have a 70% chance to hit. Also, units on lower ground
cannot see higher ground but will counterattack any units that are attacking from higher terrain (even if the
higher terrain is not visible.) Using units with longer ranges, such as Siege Tanks, on high ground areas gives
them a better field of vision and makes them much less vulnerable to attack.