Tower Defense

A playbook for tower defense, enemy pathing, wave spawning, tower targeting, and the economy that ties them together. This is a compositional skill: it orchestrates pathing, AI, and UI into a TD loop. It does not re-teach pathfinding; it defines the systems and the balance levers (DPS vs. HP vs. income) that decide whether a TD is tense or trivial.

When to use

• Use when building a game where the player places towers that automatically attack waves of enemies following a path, spends earned currency to expand/upgrade, and loses if too many enemies leak through.
• Use when designing wave composition/pacing, tower targeting priorities, or the gold economy.

When not to use: the player directly controls a shooter → fps-shooter. Free-form base building with needs → survival-crafting. For the pathfinding algorithm itself, use game-ai.

Core loop

Prepare (place/upgrade towers with current gold) → start the wave → enemies path toward the goal while towers auto-fire → earn gold from kills → survive the wave → repeat against a harder one. The tension is a planning puzzle: is my current DPS enough for what's coming, and can I afford the answer?

Must-have systems

1. Enemy path, waypoint lanes, or grid + pathfinding for maze TD (refs).
2. Wave spawner, timed, scripted sequences of enemy types with per-wave scaling.
3. Towers, range, fire rate, damage, projectile/hitscan, splash; placement validity.
4. Targeting, per-tower priority (first/last/closest/strongest/weakest) (refs).
5. Economy, gold from kills + wave bonuses; tower/upgrade costs; sell refund.
6. Lives / leak, enemies reaching the goal cost lives; 0 = game over.
7. Wave/prep UI, lives, gold, next-wave preview, start-next-wave control.

Design knobs