TD, or Tower Defense, is a foundational game genre where players strategically place defensive structures along enemy paths to prevent them from reaching a goal. Core mechanics involve resource management, tower upgrades, and wave-based enemy assaults. Its design emphasizes spatial reasoning, tactical planning, and incremental challenge scaling. Symbolically, TD represents control over chaos through systematic defense, appealing to players who enjoy puzzle-like strategy and optimization. The genre's longevity stems from its clear objectives, satisfying feedback loops, and adaptability across platforms from mobile to PC.