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+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Firefox Extension Downloader</title>
+    <style>
+        :root {
+            --bg-color: #121212;
+            --surface-color: #1e1e1e;
+            --primary-color: #00aaff;
+            --primary-hover: #0088cc;
+            --text-color: #e0e0e0;
+            --border-color: #333;
+            --error-color: #ff4d4d;
+            --success-color: #4dff4d;
+        }
+        @import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;600&display=swap');
+        * { box-sizing: border-box; margin: 0; padding: 0; }
+        html, body { height: 100%; }
+        body {
+            font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
+            background-color: var(--bg-color);
+            color: var(--text-color);
+            display: grid;
+            place-items: center;
+            padding: 1rem;
+        }
+        main {
+            width: 100%;
+            max-width: 500px;
+            background-color: var(--surface-color);
+            padding: 2.5rem 2rem;
+            border-radius: 12px;
+            border: 1px solid var(--border-color);
+            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
+            text-align: center;
+        }
+        h1 {
+            font-size: 1.75rem;
+            margin-bottom: 0.5rem;
+            font-weight: 600;
+        }
+        p {
+            margin-bottom: 1.5rem;
+            color: #aaa;
+        }
+        #dl-form {
+            display: flex;
+            flex-direction: column;
+            gap: 1rem;
+        }
+        #addon-url {
+            width: 100%;
+            padding: 0.75rem 1rem;
+            background-color: var(--bg-color);
+            border: 1px solid var(--border-color);
+            border-radius: 8px;
+            color: var(--text-color);
+            font-size: 1rem;
+            outline: none;
+            transition: border-color 0.2s, box-shadow 0.2s;
+        }
+        #addon-url:focus {
+            border-color: var(--primary-color);
+            box-shadow: 0 0 0 3px rgba(0, 170, 255, 0.2);
+        }
+        button {
+            padding: 0.75rem 1rem;
+            background-color: var(--primary-color);
+            color: #fff;
+            border: none;
+            border-radius: 8px;
+            font-size: 1rem;
+            font-weight: 600;
+            cursor: pointer;
+            transition: background-color 0.2s;
+        }
+        button:hover, button:focus {
+            background-color: var(--primary-hover);
+            outline: none;
+        }
+        #status {
+            margin-top: 1.5rem;
+            margin-bottom: -1rem; /* prevent layout shift */
+            min-height: 1.2em;
+            font-weight: 600;
+        }
+        #status.error { color: var(--error-color); }
+        #status.success { color: var(--success-color); }
+    </style>
+</head>
+<body>
+    <main>
+        <h1>Extension Downloader</h1>
+        <p>Master, provide a Firefox Add-on Store URL to download its <code>.xpi</code> source file.</p>
+        <form id="dl-form">
+            <input type="url" id="addon-url" placeholder="https://addons.mozilla.org/..." required autocomplete="off">
+            <button type="submit">Download Source</button>
+        </form>
+        <p id="status"></p>
+    </main>
+    <script>
+        document.getElementById('dl-form').addEventListener('submit', e => {
+            e.preventDefault();
+            const status = document.getElementById('status');
+            status.className = ''; status.textContent = 'Acquiring target...';
+            try {
+                fetch(`https://addons.mozilla.org/api/v5/addons/addon/${document.getElementById('addon-url').value.match(/\/addon\/([^/]+)/)[1]}/`)
+                    .then(res => res.ok ? res.json() : Promise.reject(new Error(`Server responded ${res.status}`)))
+                    .then(data => {
+                        const a = document.createElement('a');
+                        a.href = data.current_version.file.url;
+                        a.download = a.href.split('/').pop();
+                        document.body.appendChild(a).click();
+                        document.body.removeChild(a);
+                        status.className = 'success';
+                        status.textContent = `Download initiated for ${a.download}.`;
+                    })
+                    .catch(err => { status.className = 'error'; status.textContent = `Error: ${err.message}.`; })
+                    .finally(() => setTimeout(() => { status.textContent = ''; status.className = ''; }, 5000));
+            } catch (err) {
+                status.className = 'error'; status.textContent = 'Error: Invalid URL format.';
+                setTimeout(() => { status.textContent = ''; status.className = ''; }, 5000);
+            }
+        });
+    </script>
+</body>
+</html>
