Source code for the Chombit Chess video game, an API for chess-playing engines, a port of the Micro-Max algorithm, and a console for testing engines. Everything is written in the Hybrix language.
What is Hybrix? Hybrix is an educational virtual computer with an emulator and full development environment that run in your web browser. Its custom 32-bit CPU executes 2,400,000 instructions per second with only 256 kilobytes of RAM. Like a classic computer, these specs encourage programs that a single person can understand with minimal reliance on frameworks. Deterministic CPU timings allow performance to be measured precisely and reproducibly. These qualities make it an interesting platform for coding chess algorithms.
Click to see it run!
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A full chess video game: pieces on a perspective board, a mouse-driven wand for picking squares, legal destinations highlighted on selection, and a status bar for undo, new game, and switching either side between Human and Robot. The Robot uses Micro-Max (see below), with difficulty controlling the search time (Easy = 200 ms, Medium = 6 secs, Hard = 30 secs). Artwork and sound resources are in the Hybrix Designer's native formats, but will be made inspectable later.
For more details about this game, see the Hybrix website docs.
| Filename | Description |
|---|---|
| chombit-chess/main.hyb | Game state machine, click handling, and undo history |
| chombit-chess/gameboard.hyb | Perspective board drawing and square hit testing |
| chombit-chess/hud.hyb | Status bar, its questions, and the about box |
| chombit-chess/selection.hyb | Piece selection and legal target marks |
| chombit-chess/chess_sprites.hyb | Piece sprites and their sliding animation |
| chombit-chess/wand_actor.hyb | The pointer sprite and the square or bar column under its tip |
| chombit-chess/symbol_types.hyb | Designer symbol declarations for scenes and actor spots |
The chess_engine class defines a plug-in contract allowing a chess front end such as Chombit Chess to load a chess engine. It connects our two chess games to the two engine implementations.
The subclass defines the chess game rules, since search algorithms often implement slightly different rules. It reports board state through a chess_position object. Four engine features are declared separately, so a subclass isn't obligated to implement them all:
| Feature | Enables |
|---|---|
load_position() |
Loading and saving board states, or puzzles |
undo_move() |
Taking back one or more moves |
collect_moves() |
Highlighting legal destinations in a GUI |
find_move() |
The search algorithm for computer play |
The reference_chess_engine class implements all four features, using the orthodox chess rules including check, checkmate, and stalemate. It models the full state for a human-vs-human game. Its search algorithm is a minimal placeholder that simply returns the first legal move it finds.
| Filename | Description |
|---|---|
| engine-api/chess_engine.hyb | Enums, the chess_position record, and the plug-in base class |
| engine-api/reference_chess_engine.hyb | Reference subclass implementing all four features |
To write your own engine, subclass chess_engine, set the can_ flags for the features you support, then fill in the hooks. If it plays well, we may incorporate it into the official Chombit Chess game as an alternate computer player.
H.G. Muller's Micro-Max is a well-known chess program that fits in only 2,000 characters of C source code. We've ported version 3.2 to Hybrix with his permission; details in this TalkChess thread.
The algorithm is well explained by the author's own documentation:
Fitting the algorithm into 256 kilobytes required a few departures from the original:
- The transposition table holds 8,192 entries rather than millions. Two probe and replacement schemes are compiled in and selected by a constant: the original 3.2 scan of consecutive slots, and the shallowest-of-two replacement that Muller recommended for a table this small.
load_position()is omitted, because Micro-Max state cannot be rebuilt exactly from achess_positionrecord. A game begins atload_new_game()and continues through accepted moves.- Micro-Max traits are preserved rather than modernized. A pawn always promotes to a queen, for example.
| Filename | Description |
|---|---|
| micromax/micromax.hyb | Micro-Max 3.2 ported to the Hybrix language |
Click to see it run!
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A HASCII console chess game in the spirit of the original Micro-Max stdio loop. Type a move like e2e4 and press ENTER, or press ENTER alone to let the engine move, or ESC to stop it thinking. Each computer move reports its node count and elapsed milliseconds.
This is the simplest way to test a new chess_engine subclass. By setting the node_budget constant with budget_ms disabled (0), you can get fully deterministic output.
| Filename | Description |
|---|---|
| chess-console/main.hyb | Text console front end for typed moves |
BSD-3-Clause license; see NOTICE.txt for legal details.