# Squadron TD Clone — Game Design Document

## Overview

A 1–8 player cooperative/competitive tower defense game inspired by Squadron Tower Defense (SC2 Arcade). Players choose a **builder race**, place towers that transform into fighters during combat, manage a worker economy, and optionally send bonus enemies at opponents. Survive 31 waves to win.

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## Core Loop

```
Pick builder race → Place towers → Wave combat → Collect income → Send enemies → Repeat
```

Each round:
1. **Build phase** — players spend minerals to place/upgrade towers.
2. **Combat phase** — towers transform into fighter units and engage the wave automatically.
3. **Income phase** — mineral income is paid out based on cumulative sends and upgrades.

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## Player Count & Teams

- **Solo (1):** one lane, self-sends only.
- **Co-op (2–4):** shared team security system, each player holds their own lane.
- **PvP (4v4):** two teams; players send enemies across to opponents.

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## Lanes & Security System

- Each player defends a **lane** of creep pathing.
- All lanes converge on the **Security System** (shared HP pool per team).
- If the Security System reaches 0 HP, the team loses.

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## Builder Races

Each race has a unique tower roster, stats profile, and upgrade tree. All races are balanced around different timing windows.

| Race | Profile | Strengths |
|---|---|---|
| Ghost | High damage, low HP (glass cannon) | Early & late game |
| Fortress | Low damage, high HP + buffs/debuffs | Early & mid game |
| Phantom | Evasive, mixed melee/ranged | Mid & late game |
| Ancient | Slow, extremely high damage AoE | Late game |

Each race has roughly **8–12 towers** in a **tier tree**:
- Tier 1: base units (cheap, unlocked immediately)
- Tier 2: upgrades from Tier 1 (requires minerals + sometimes gas)
- Tier 3: capstone units (high cost, powerful)

Upgrading a tower **in place** morphs the sprite and updates stats.

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## Towers / Fighters

Towers placed during build phase transform into **fighter units** during combat. Fighters are fully AI-controlled.

### Tower Data Fields

| Field | Type | Notes |
|---|---|---|
| id | String | Unique identifier |
| race | String | Builder race |
| tier | Int | 1–3 |
| cost_minerals | Int | Build cost |
| cost_gas | Int | Upgrade cost (0 for tier 1) |
| hp | Int | Fighter HP |
| armor_type | Enum | Light / Medium / Heavy / Unarmored |
| attack_type | Enum | Normal / Explosive / Concussive / Chaos |
| damage | Int | Base damage per hit |
| attack_speed | Float | Attacks per second |
| range | Float | Attack range in tiles |
| move_speed | Float | Fighter move speed |
| upgrades_to | String? | Next tier tower ID |
| strong_vs_waves | [Int] | Wave numbers this unit excels at |

### Armor/Attack Type Matrix (damage multipliers)

|  | Normal | Explosive | Concussive | Chaos |
|---|---|---|---|---|
| Light | 100% | 75% | 150% | 100% |
| Medium | 100% | 100% | 75% | 100% |
| Heavy | 100% | 150% | 50% | 100% |
| Unarmored | 100% | 75% | 100% | 100% |

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## Economy

### Minerals
- Passive income per round (base ~50, slight scaling).
- Bonus income earned cumulatively by **sending** units or upgrading the Security System.
- Spent on: building/upgrading towers.

### Gas
- Generated by **worker units** each round.
- Spent on: sends, Security System upgrades, supply cap raises.

### Workers
- Each player starts with a few workers.
- Build more workers early — aim for ~20 by wave 25.
- Workers cost minerals; balance worker vs. tower investment.

### Sends
- Spend gas to send bonus creeps into an opponent's lane (or self in solo).
- Each send type adds a permanent per-round income bonus.
- Send income is cumulative — early sending snowballs economy.

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## Waves

31 total waves. Each wave definition:

| Field | Notes |
|---|---|
| wave_number | 1–31 |
| creep_type | Enum: Light, Armored, Mixed, Boss |
| creep_armor | Armor type |
| creep_count | Number of units |
| creep_hp | Base HP |
| creep_speed | Move speed |
| bounty | Minerals per kill |

- Waves 1–10: economy building phase, lighter creeps.
- Waves 11–20: increasing pressure.
- Waves 21–30: heavy creeps, economy should be near max.
- Wave 31: boss/final wave.

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## Security System

- Shared team HP pool (e.g. 20 HP per player slot).
- Creeps reaching the exit drain 1–5 HP depending on type.
- Can be upgraded for gas (increases max HP and/or armor).

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## Victory / Defeat

- **Win:** Survive all 31 waves with Security System HP > 0.
- **Lose:** Security System reaches 0 HP.
- Scored by: waves survived, sends sent, Security System HP remaining.

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## Stretch Features (post-MVP)

- Chaos Mode (random race each round)
- Spectator mode
- Replay system
- Persistent leaderboard