Variant aspects

Board Geometry

Rectangular

- Micro chess (4x4)
- Mini chess (5x5)
- Western Chess (8x8)
- Capablanca Chess (8x10)
- Grand Chess (10x10)
- Terachess (16x16)

Historical

- Xiang Qi
- Shogi
- Janggi
- Chaturanga
- Shatranj

Other

- Omega Chess (10x10 + 4 extra squares)
- Alice Chess (two 8x8 boards)
- Fortress (8x8 + 8x2x4 + 4x4x4)
- Four-player chess (8x8 + 8x3x4)
- Hexagonal (nxm)
- Triangular (n)
- Pentagons?
- Circular
- Cylindrical
- Vertical Mirror
- Torus
- Möbius?
- Cube (Chess 360)
- Sphere
- 3D
- Infinite (mostly theoretical)

Armies / Piece set

- Definition of each piece:
	- Initial position
	- Extra initial movement (pawns)
	- How it moves or captures
        - Slider
        - Leeper
        - Hopper
        - Rider
        - Locust
	- Is it royal (cannot be put or left in check)
	- What it promotes to when reaching promotion zone
	- Special rules involving a combination of pieces:
		- Castle
		- En passant
	- Abbreviation (For game annotations)
	- Visual Representation (Image)
    - Description
        - Name(s)
        - Ethytmology
        - Origins
- Definition of each army, if different for different players

Promotion zones

- Last rank
- Last 3 ranks
- Half-way (like pawns promoting to soldiers past the river in Xiang Qi)
- 8th rank (like in Four-people chess)
- Specific region (central 2x2 square)

Number of players/armies, teams and boards

- Classic Bughouse: 2 teams of 2 players, with 2 boards
- Bughouse 3 or 4: 2 teams of 3 or 4 players, with 3 or 4 boards
- Three-player chess
- Four-player chess (teams or free for all)

Game Mechanics

- Drop Chess
	- Shogi
	- Crazyhouse
	- Chessgi
- Double or more moves:
	- Marseillais Chess
	- Extra Move Chess
	- Twinmove Chess
	- Progressive Chess
- Anti-King

Capture

- Regular
- Decay (pieces soon after capture)
- Atomic (explodes around)

Visibility

- Fully Visible (normal)
- Fog of war (discover as you play)
- Blindfolded (rely on player's memory)

Initial Setup

- Preset (Most variations)
- Random (Fisher variation)
- Placement (Players place pieces in turns)
- Inverse placement (Opponent places your pieces)
- Blind Placement (Cannot see Opponent's placement)

Win Goal for 2 player games

- Mate (or capture) one or several or all present royal pieces
- Stalemate (Xiang Qi or Antichess)
- Capture all material (Horde)
- Lose all material (Antichess)
- A designated piece reaches a region
	- King of the hill - King reaches middle 2x2 square in a 8x8
	- Racing Kings (King reaches last rank + King cannot be put in check)
- Carry out n checks (Three-check)

Win Goal for multiple players

- Win against all opponents (4 player chess)
- Win against one opponent from opposite team (bughouse)

Draw conditions

- 50 move rule (no pawn moves or captures)
- Three repetition rule
- Condition to win can no longer be met (mate not possible)

Time controls

- Sudden Death (5 min, 30 min, 1h)
- Increment / move (3 min + 2 sec / move)
- Time per move (1 min / move)

Implementation Ideas

- Serverless, Peer-to-peer
	- Game sharing via URL
	- Game definitions export / import
	- Common Variations and Graphic Assets
- Restrict geometry to single board rectangular
- Restrict to 2 players
- Restrict Visibility to visible
- Restrict Initial Setup to preset
- Restrict Capture and Mechanics to normal