Fog of war
Hides parts of the map the player has not scouted or cannot currently see, typically in two layers: unexplored (fully black) and explored-but-not-visible (terrain shown, units hidden). Designers use it to make information a resource — scouting becomes an action worth spending on, ambushes and misdirection become possible, and the map itself gains replay tension. In strategy games it drives the entire reconnaissance layer; removing it collapses whole strategic dimensions. Implementation is grid visibility: line-of-sight checks, vision radii per unit, and efficient dirty-region updates so hundreds of units do not recompute visibility every frame. Design decisions: does vision persist for terrain, do allied units share vision, and can effects (recon sweeps, watchtowers) reveal areas temporarily. Pitfall in single-player: AI that ignores fog and 'knows' your positions destroys trust the moment players notice. The exploration-side variant is map reveal: persistent fog that clears for good as players uncover the world map, rewarding exploration rather than modeling battlefield information.
- Dev effort: Medium
- Timing: Real-time or turn-based
- Common in: strategy, tactics
Seen in
- Civilization VI
- StarCraft II
- Age of Empires II