tower-defense

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

Patterns

1. Wave spawner (timed, data-driven)

# Pseudocode. A wave is data: a list of (enemy_type, count, spacing). Spawn over time.
wave = [ ("grunt", 10, 0.5), ("runner", 

2. Tower targeting (filter to range, then pick by priority)

3. "Can this lane hold?" sanity check (DPS vs. HP)

Pitfalls / failure modes

• Enemy HP scales slower than player income/DPS → game trivializes after a few waves. Tune the HP curve against the income curve (refs).
• One dominant tower/strategy → no decisions. Add enemy types that hard-counter builds (armored vs. rapid-fire, flying vs. ground-only) and diminishing upgrade returns.
• Maze TD that can fully block the goal → enemies get stuck/softlock. Forbid placements that sever the path; recompute paths when towers change (refs).
• No next-wave telegraph → specials feel random and unfair. Preview upcoming composition.
• Per-frame movement unscaled by dt → speed varies with frame rate. Scale steering by dt.
• Leaks only cost lives, not gold → leaking is sometimes optimal. Make leaks lose bounty too.
• Monotonic difficulty ramp → exhausting. Pace spikes and breathers.

Composition (build it from these skills)

• Pathing: game-ai for A*/flow-field/steering; for fixed lanes, simple waypoint following.
• Enemy movement: godot-2d-movement (or engine equivalent) to move along the path; unity-navmesh for nav-based pathing.
• Map: godot-tilemap / unity-tilemap-2d for the grid/lanes; level-design for map layouts.
• Data: godot-resources / unity-scriptableobjects to define towers, enemies, and waves as assets.
• UI: game-ui-ux for HUD layout, scaling, and the build menu; godot-ui-control for the concrete widgets (lives, gold, wave preview).
• Polish: audio-design for fire/hit/leak sound cues.

References

• For path representations (waypoints / A* / flow fields), targeting modes, DPS and economy math, enemy scaling, and wave pacing, read references/balancing.md.