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Writing a Chess Engine

I’ve written a dependency-free chess engine library in my free time between classes.

Why write a Chess engine?

Above all, this video by Tom7 is my inspiration for this project. He’s absolutely brilliant and I implore you to watch his content.

I love chess a lot. It’s definitely one of my favorite games ever. However, I’ve always been disappointed when trying to write programs that play chess digitally (particularly in a compiled language). Although several amazing engines exist, it’s near impossible to find a neat library for chess-related-programming that runs on everything.

chess-engine is a solution to my problem. If you want a chess engine that runs on embedded devices, the terminal, the desktop (with a gui), and the web, this is probably your best bet.

How does it work?

This particular AI (along with most other chess AIs) works using the Minimax algorithm, along with Alpha-Beta pruning for optimization.

Now, let’s unpack that.

The Minimax algorithm essentially iterates through all possible moves recursively, and evaluates all of the boards after the moves are played. If the board is more favorable, it will encourage playing its parent move, but if a board is less favorable, then it will select against playing a given move.


Additionally, when the AI attempts to see past just the current board, it will assume the human always responds with the best moves. As a result, the computer almost never blunders. This allows the computer to almost always play objectively better moves than the player.

Embedded in the Web

Because it has zero dependencies, it’s extremely simple to embed in the web browser using wasm. Try playing it yourself!

Average AI Setting:

Abusing Minimax

Because Minimax works by simply maximizing the AI’s material advantage over the player, it’s incredibly simple to abuse the algorithm by changing what it is maximizing.

Here, for example, is the opposite of a good AI. This AI tries to maximize YOUR material value, and will desperately try to offer you its pieces while still making legal moves. Worst AI Setting:

Chess Variants

Additionally, builtin, chess-engine offers an incredibly simple chess variant called Horde, which I find very fun.

Horde Chess Variant:

Additionally, chess-engine supports getting all of the legal moves for a player. So, naturally, I had to add a random-move AI.

Random AI Setting: