Exchange
by Dead Letter Games
A turn-based roguelike strategy game that reimagines chess as a tactical RPG. Pieces have hit points, abilities, and persistence across battles. Navigate a branching map, collect relics, and dethrone the enemy King.
The Core Concept
Exchange takes the familiar framework of chess and transforms it into something entirely new:
- Pieces have HP - Attacks deal damage based on dice rolls; pieces don't die in one hit
- One action per turn - Each turn, ONE piece performs ONE action: Move, Attack, or Ability
- Roguelike progression - Navigate through acts, collect relics, and face escalating challenges
- Persistent army - Your pieces carry their HP and cooldowns between battles
Combat Rules
Turn Economy
Each turn, exactly one piece may act. An action is one of:
- Move - Standard chess-inspired movement patterns
- Base Attack - Deal damage to an enemy (replaces movement)
- Use Ability - Unique power for each piece type
No chaining allowed, except for the Knight's special rule.
Damage Calculation
Total Damage = Base Damage + Dice Roll (1d6, clamped 1-6)
Modifiers affect your roll:
- Entered threat zone this turn: -1 to roll
- Enemy King is threatened: +1 to your roll
- Royal Decree active: +1 to all allied rolls
Victory Condition
- Win: Enemy King reaches 0 HP
- Lose: Your King reaches 0 HP
Piece Stats
| Piece |
HP |
Base Damage |
Attack Range |
| King |
15 |
1 |
Adjacent (all 8 directions) |
| Queen |
10 |
3 |
Up to 3 tiles in any direction |
| Rook |
13 |
2 |
Up to 2 tiles orthogonally |
| Knight |
11 |
2 |
Adjacent only (but can move+attack) |
| Bishop |
10 |
2 |
Up to 3 tiles diagonally (not adjacent) |
| Pawn |
7 |
1 |
Diagonal-adjacent forward only |
Abilities
Each piece type has a unique ability that replaces movement and attacks:
| Piece |
Ability |
Cooldown |
Effect |
| King |
Royal Decree |
Once/match |
All allied combat rolls gain +1 until your next turn |
| Queen |
Overextend |
3 turns |
Move, then attack. Queen takes 2 self-damage afterward |
| Rook |
Interpose |
3 turns |
Damage to adjacent allies is split between ally and Rook |
| Bishop |
Consecration |
3 turns |
Heal a diagonal ally for 1d6 HP (cannot target self) |
| Knight |
Skirmish |
3 turns |
Attack, then reposition 1 tile |
| Pawn |
Advance |
1 turn |
Move forward one additional tile (cannot use consecutively) |
Knight Special Rule
The Knight is unique: it may move then attack in the same turn.
- Must move first
- Attack must be adjacent to landing square
- Cannot attack without moving first
- Using an ability replaces this behavior
Threat Zones
- A Threat Zone is any tile a piece could attack from its current position
- Threat zones are always visible on the board
- Penalty: Moving into a threat zone applies -1 to your next combat roll
- King Safety: The King cannot move into threatened tiles
- King Threatened: If your King ends a turn in a threat zone, the enemy gains +1 to their next attack
Map System
Exchange features a Slay the Spire-style branching map that offers player agency:
Structure
- 3 Acts + Final Boss
- Node tree flows left to right
- Player chooses their path through branching nodes
- All paths converge at the Boss node
Node Types
| Node |
Description |
| Combat |
Standard battle against enemy chess army |
| Elite |
Harder combat with better rewards |
| Treasure |
Free relic or resource pickup |
| Shop |
Spend coins on relics, healing, upgrades |
| Event |
Random encounter with risk/reward choices |
| Boss |
End-of-act mandatory fight |
AI Difficulty Scaling
The enemy AI grows smarter as you progress:
| Act |
Search Depth |
Behavior |
| Act 1 |
2-ply |
Basic tactical awareness |
| Act 2 |
3-ply |
Sees your response to their moves |
| Act 3 |
4-ply |
Deep strategic planning |
| Final Boss |
5-ply |
Maximum difficulty |
Relics
Relics are passive items that bend the rules in your favor. Categories include:
Dice Relics
- Ivory Die - First roll each match cannot be below 2
- Weighted Die - Dice rolls of 6 deal +1 damage
- Fate Weights - First roll each match is treated as 6
Formation Relics
- Battle Standard - Adjacent allies take -1 damage
- Command Flag - Adjacent allies gain +1 dice on attacks
- Shield Emblem - Adjacent allies ignore threat penalties
Rule-Benders (Rare)
- Double-Headed Knight - First non-Knight attack may move then attack
- Split Square - First piece each match ignores move/attack exclusivity
- False Crown - First time the King would die, it remains at 1 HP
Boss Modifiers
Each act boss introduces a unique rule that changes combat:
- Act 1 Boss: Threat penalties are -2 instead of -1
- Act 2 Boss: Enemies adjacent to allies take -1 damage
- Act 3 Boss: Enemy King may move into threatened tiles
- Final Boss: Player King is always considered threatened (+1 to all enemy rolls)
Technical Architecture
Tech Stack
- Engine: Godot 4.5+ with .NET 8.0
- Language: C# 12 with file-scoped namespaces
- Pattern: Composition over inheritance, event-driven communication
AI System
- True N-ply minimax search with alpha-beta pruning
- Transposition tables with Zobrist hashing for position caching
- Parallel search using "Young Brothers Wait" strategy
- Pondering during player's turn for faster response
- MVV-LVA move ordering for efficient pruning
Namespace Structure
Exchange/
├── Core/ # Enums, data structures, game state
├── Board/ # Tile and GameBoard management
├── Pieces/ # All chess piece implementations
├── Combat/ # Dice rolling and combat resolution
├── Controllers/ # Game flow, turns, AI
├── AI/ # Minimax engine, transposition tables
├── Map/ # Roguelike map generation
└── UI/ # User interface components
Systems In Development
Implemented
Upcoming
Building
dotnet build
Run from Godot Editor or build with:
godot --export-release "platform" output_path
License
All rights reserved. Copyright Dead Letter Games.