Tower Defense Lane Denial

Attackers follow a path and rarely fight back directly, while defenders are immobile and pay for range, damage type and rate of fire. Resources come from kills, so each wave funds preparation for the next. Difficulty climbs through waves with different resistances and speeds, and the real decisions concern where to spend, when to upgrade rather than expand, and how far placement can lengthen the route.

Warcraft III: Reign of Chaos supplied the tools in 2003, and the genre grew inside its custom map scene rather than being designed as a product; Blizzard Entertainment built the editor and players built the form. Older ancestors are frequently cited, including arcade games about defending a position and comparable maps in earlier strategy titles. Free tools plus an audience of map makers turned an idea into a category.

Spinning out of a mod scene into standalone games happened quickly, and the format suited browsers and phones unusually well because it needs no reflexes and pauses gracefully. Depth and repetition are the costs. Optimal layouts exist and can be looked up, which reduces strategy to executing a known answer, so later designs add randomised waves, restricted placement or hero units to keep decisions live.