Eight games about holding a line without ever moving. You buy a tower, you put it somewhere, and then you watch: all of the skill is in the order you buy and the place you choose. Battle of Antarctica keeps the money tight enough that one wrong early purchase costs the map. Kiz Flower Defense makes you grow an economy instead of earning it from kills, since flowers attract lumins and lumins buy units. The Protectors: Revenge of Saarshe marks the ground green where a tower will fit, which more of them should do. Warzone Tower Defense Extended and Red Storm Defense are the long ones, for an evening rather than a coffee break.
8 games, free to play in the browser.