diff --git a/DISCOVER/404.html b/DISCOVER/404.html
index 543b5734..a53daed2 100644
--- a/DISCOVER/404.html
+++ b/DISCOVER/404.html
@@ -1,170 +1,37 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-  <meta charset="UTF-8" />
-  <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
-  <title>404 - Not Found</title>
-  <style>
-    * {
-      box-sizing: border-box;
-      margin: 0;
-      padding: 0;
-    }
-    body {
-      height: 100vh;
-      background: linear-gradient(135deg, black, #e4f0ff);
-      display: flex;
-      align-items: center;
-      justify-content: center;
-      font-family: 'Segoe UI', sans-serif;
-      overflow: hidden;
-      position: relative;
-    }
-
-    .light-blur {
-      position: absolute;
-      width: 500px;
-      height: 500px;
-      background: radial-gradient(circle at center, transparent);
-      border-radius: 50%;
-      filter: blur(80px);
-      top: 20%;
-      left: 10%;
-      animation: drift 10s ease-in-out infinite alternate;
-      z-index: 0;
-    }
-
-    @keyframes drift {
-      0%   { transform: translate(0, 0); }
-      100% { transform: translate(60px, 30px); }
-    }
-
-    .glass-card {
-      background: rgba(255, 255, 255, 0.25);
-      backdrop-filter: blur(12px);
-      -webkit-backdrop-filter: blur(12px);
-      padding: 2.5rem 3rem;
-      border-radius: 20px;
-      border: 1px solid rgba(255, 255, 255, 0.3);
-      max-width: 500px;
-      text-align: center;
-      z-index: 1;
-      box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
-    }
-
-    h1 {
-      font-size: 2.5em;
-      color: rgb(52, 51, 51);
-      margin-bottom: 0.5rem;
-    }
-
-    p {
-      font-size: 1.1em;
-      color: rgb(52, 51, 51);
-      margin-bottom: 1.4rem;
-    }
-
-    a {
-      display: inline-block;
-      margin: 0.4rem;
-      padding: 0.6rem 1rem;
-      border-radius: 8px;
-      text-decoration: none;
-      background: #d0bfff;
-      color: #1f1f1f;
-      font-weight: 600;
-      transition: background 0.3s ease;
-    }
-
-    a:hover {
-      background: #c1aaff;
-    }
-
-    select {
-      margin-top: 1rem;
-      padding: 0.5rem;
-      border-radius: 6px;
-      border: 1px solid #ccc;
-      font-size: 1em;
-      background: #fff;
-    }
-  </style>
-</head>
-<body>
-  <div class="light-blur"></div>
-  <div class="glass-card">
-    <h1 id="title">404 - Page Not Found</h1>
-    <p id="message">This page might’ve wandered off or was never here at all.</p>
-    <p id="suggestion">Maybe it was deleted, renamed, or never existed in the first place.</p>
-    <p><strong id="what-do">What can you do?</strong></p>
-    <a href="./intro.html" id="home">⬅️ Back to Home</a>
-    <a href="https://github.com/numfocus/DISCOVER-Cookbook/issues" id="report">🐞 Report the Issue</a>
-
-    <div>
-      <label for="language-switcher" style="display:block; margin-top:1.5rem; color:#444;">🌐 Switch Language:</label>
-      <select id="language-switcher">
-        <option value="en">English</option>
-        <option value="es">Español</option>
-      </select>
-    </div>
-
-    <p id="footer" style="margin-top: 1.2rem;">If you think this is an error, let us know by creating an issue.</p>
-  </div>
-
-  <script>
-    const translations = {
-      en: {
-        title: "404 - Page Not Found",
-        message: "This page might’ve wandered off or was never here at all.",
-        suggestion: "Maybe it was deleted, renamed, or never existed in the first place.",
-        whatDo: "What can you do?",
-        home: "⬅️ Back to Home",
-        report: "🐞 Report the Issue",
-        footer: "If you think this is an error, let us know by creating an issue."
-      },
-      es: {
-        title: "404 - Página no encontrada",
-        message: "Esta página se ha perdido o nunca existió.",
-        suggestion: "Tal vez fue eliminada, renombrada o nunca existió.",
-        whatDo: "¿Qué puedes hacer?",
-        home: "⬅️ Volver al inicio",
-        report: "🐞 Informar del problema",
-        footer: "Si crees que esto es un error, infórmanos creando un issue."
-      }
-    };
-
-    function detectLanguage() {
-      const pathLang = location.pathname.split("/")[1];
-      const refLang = new URL(document.referrer || "", location.origin).pathname.split("/")[1];
-      const storedLang = localStorage.getItem("preferredLang");
-      return translations[pathLang]
-        ? pathLang
-        : translations[refLang]
-        ? refLang
-        : translations[storedLang]
-        ? storedLang
-        : "en";
-    }
-
-    function applyLanguage(lang) {
-      const t = translations[lang] || translations["en"];
-      document.getElementById("title").textContent = t.title;
-      document.getElementById("message").textContent = t.message;
-      document.getElementById("suggestion").textContent = t.suggestion;
-      document.getElementById("what-do").textContent = t.whatDo;
-      document.getElementById("home").textContent = t.home;
-      document.getElementById("report").textContent = t.report;
-      document.getElementById("footer").textContent = t.footer;
-      document.getElementById("language-switcher").value = lang;
-      localStorage.setItem("preferredLang", lang);
-    }
-
-    const initialLang = detectLanguage();
-    applyLanguage(initialLang);
-
-    document.getElementById("language-switcher").addEventListener("change", function () {
-      applyLanguage(this.value);
-    });
-  </script>
-</body>
-</html>
+{% extends "sphinx_book_theme/layout.html" %}
+
+{% block content %}
+
+<div style="text-align:center; padding:60px 20px;">
+  <h1 style="font-size:80px; color:#2e7d32; margin-bottom:10px;">404</h1>
+  <h2>Oops! Page not found</h2>
+
+  <p style="max-width:500px; margin:20px auto; color:#555;">
+    The page you are looking for doesn't exist or has been moved.
+    Let's get you back to the DISCOVER Cookbook.
+  </p>
+
+  <a href="/" style="
+      background:#2e7d32;
+      color:white;
+      padding:12px 24px;
+      border-radius:8px;
+      text-decoration:none;
+      margin:10px;
+      display:inline-block;">
+      Go Home
+  </a>
+
+  <a href="/intro.html" style="
+      border:2px solid #2e7d32;
+      color:#2e7d32;
+      padding:12px 24px;
+      border-radius:8px;
+      text-decoration:none;
+      margin:10px;
+      display:inline-block;">
+      Start Reading
+  </a>
+</div>
+
+{% endblock %}
diff --git a/_build/logs/myst.build.json b/_build/logs/myst.build.json
new file mode 100644
index 00000000..55733548
--- /dev/null
+++ b/_build/logs/myst.build.json
@@ -0,0 +1,31 @@
+{
+  "input": {
+    "files": [
+      "DISCOVER"
+    ],
+    "opts": {
+      "execute": false,
+      "executeParallel": 11,
+      "pdf": false,
+      "tex": false,
+      "typst": false,
+      "docx": false,
+      "md": false,
+      "xml": false,
+      "meca": false,
+      "cff": false,
+      "site": false,
+      "html": false,
+      "all": false,
+      "doiBib": false,
+      "watch": false,
+      "force": false,
+      "checkLinks": false,
+      "strict": false,
+      "ci": false,
+      "maxSizeWebp": 1572864,
+      "keepHost": false
+    }
+  },
+  "exports": []
+}
\ No newline at end of file
