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<ol class="chapter"><li class="chapter-item expanded "><a href="chess-engine.html"><strong aria-hidden="true">1.</strong> chess-engine</a></li></ol>
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<h1 id="chess-engine"><a class="header" href="#chess-engine">chess-engine</a></h1>
<p>A pure Rust, dependency-free chess engine built to run anywhere.</p>
<h2 id="why-write-a-chess-engine"><a class="header" href="#why-write-a-chess-engine">Why write a Chess engine?</a></h2>
<p>I love chess a <em>lot</em>. It's definitely one of my favorite games ever. However, I've always been disappointed when trying to play chess digitally. Although wonderful websites like <a href="https://chess.com/">chess.com</a> and <a href="https://lichess.org/">lichess</a> exist, it's near impossible to find something that runs on everything.</p>
<p>chess-engine is a solution to my problem. If you want a chess engine that runs on embedded devices, the terminal, <a href="https://github.com/adam-mcdaniel/chess-engine/tree/main/examples/chess-gui">the desktop (with a gui)</a>, <em>and</em> <a href="https://adam-mcdaniel.github.io/chess-engine/docs/book/index.html#average-ai">the web</a>, this is probably your best bet.</p>
<h2 id="how-does-it-work"><a class="header" href="#how-does-it-work">How does it work?</a></h2>
<p>This particular AI works using the <a href="https://en.wikipedia.org/wiki/Minimax">Minimax algorithm</a>, along with <a href="https://en.wikipedia.org/wiki/Alpha%E2%80%93beta_pruning">Alpha-Beta pruning</a> for optimization.</p>
<p>Now, let's unpack that.</p>
<p>The Minimax algorithm essentially iterates through all possible moves recursively, and assumes that whenever the computer plays, the human player will always respond with the best move.</p>
<p><img src="move-generation.png" alt="Move generation" /></p>
<p>This allows the computer to almost always play objectively better moves than the player.</p>
<p><img src="mini-max.jpeg" alt="Minimax" /></p>
<p>As you can see with a little experimentation, it works quite well. </p>
<h4 id="average-ai"><a class="header" href="#average-ai">Average AI</a></h4>
<h5 id="keep-in-mind-this-is-at-a-low-difficulty-setting-for-speed-in-the-browser"><a class="header" href="#keep-in-mind-this-is-at-a-low-difficulty-setting-for-speed-in-the-browser">Keep in mind, this is at a low difficulty setting for speed in the browser.</a></h5>
<embed type="text/html" src="https://adam-mcdaniel.github.io/chess-engine/examples/chess-web/chess-best.html" width="420" height="420"/>
<h3 id="abusing-minimax"><a class="header" href="#abusing-minimax">Abusing Minimax</a></h3>
<p>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.</p>
<p>Here, for example, is the <strong><em>opposite</em></strong> of a good AI. This AI tries to maximize <em><strong>YOUR</strong></em> material value, and will desperately try to offer you its pieces while still making legal moves.</p>
<embed type="text/html" src="https://adam-mcdaniel.github.io/chess-engine/examples/chess-web/chess-worst.html" width="420" height="420"/>
<h2 id="other-features"><a class="header" href="#other-features">Other features</a></h2>
<p>Additionally, builtin, chess-engine offers an incredibly simple chess variant called <a href="https://www.chess.com/terms/horde-chess">Horde</a>, which I find very fun.</p>
<embed type="text/html" src="https://adam-mcdaniel.github.io/chess-engine/examples/chess-web/chess-horde.html" width="420" height="420"/>
<p>Additionally, chess-engine supports getting all of the legal moves for a player. So, naturally, I had to add a random-move AI.</p>
<embed type="text/html" src="https://adam-mcdaniel.github.io/chess-engine/examples/chess-web/chess-random.html" width="420" height="420"/>
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