Elevation

Examples:
* Hulldown possible without special "abilities" with careful placement of the units. (e.g. tank rising uphill only so far that its turret shows and not the tank's body, thus being harder target to hit, especially in a way that actually causes notable damage)
* Natural barriers (strategy games have a habit of ignoring hills and similar)
* Accuracy/range bonuses for those on higher ground, inverted for those on lower ground.

Limitations:
* Does NOT count if only affects Line-of-Sight.
* Generally only for games played from bird's eye perspective.

Notes:
* Some games may "simulate" this by using "one-sided windows" on hills and such that effectively block any weapons the game deems incapable of shooting over hills.
* Games that simply check range usually ignore hills (the tracers are seen clearly passing through hills), those that simulate the projectiles' flight paths tend to do elevation effects naturally.