diff --git a/error.html b/error.html
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index 0000000..fbebde9
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+++ b/error.html
@@ -0,0 +1,347 @@
+<!doctype html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8" />
+        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+
+        <title>Coupon Used — Derez.ai</title>
+        <meta name="robots" content="noindex, nofollow" />
+
+        <style>
+            :root {
+                --bg: #000810;
+                --bg-card: #010f20;
+                --bg-inner: #000d1a;
+                --bg-hover: #001a30;
+                --border: #0a3060;
+                --border-hi: rgba(0, 245, 255, 0.45);
+                --accent: #00f5ff;
+                --accent-dim: #002535;
+                --danger: #ff3b3b;
+                --danger-dim: #3b0000;
+                --text: #c8f0ff;
+                --text-muted: #2e6a80;
+                --radius: 8px;
+                --radius-card: 18px;
+                --shadow:
+                    0 0 0 1px rgba(0, 245, 255, 0.25),
+                    0 0 60px rgba(0, 245, 255, 0.12),
+                    0 28px 72px rgba(0, 0, 0, 0.9);
+                --max-width: 540px;
+            }
+
+            *,
+            *::before,
+            *::after {
+                box-sizing: border-box;
+                margin: 0;
+                padding: 0;
+            }
+
+            html {
+                scroll-behavior: smooth;
+                -webkit-font-smoothing: antialiased;
+            }
+
+            body {
+                font-family: "Courier New", Courier, monospace;
+                background: var(--bg);
+                color: var(--text);
+                font-size: 14px;
+                line-height: 1.6;
+                overflow-x: hidden;
+                min-height: 100vh;
+                display: flex;
+                flex-direction: column;
+            }
+
+            body::before {
+                content: "";
+                position: fixed;
+                inset: 0;
+                background:
+                    radial-gradient(
+                        ellipse 60% 50% at 25% 30%,
+                        rgba(0, 245, 255, 0.06) 0%,
+                        transparent 70%
+                    ),
+                    radial-gradient(
+                        ellipse 50% 60% at 75% 70%,
+                        rgba(0, 200, 255, 0.04) 0%,
+                        transparent 70%
+                    );
+                pointer-events: none;
+                z-index: 0;
+            }
+
+            .container {
+                max-width: var(--max-width);
+                margin: 0 auto;
+                padding: 0 24px;
+                position: relative;
+                z-index: 1;
+            }
+
+            /* ── Header ────────────────────────────────────────────── */
+            .site-header {
+                position: fixed;
+                top: 0;
+                left: 0;
+                right: 0;
+                z-index: 100;
+                background: rgba(0, 8, 16, 0.85);
+                backdrop-filter: blur(14px);
+                border-bottom: 1px solid var(--border-hi);
+            }
+
+            .site-header .container {
+                display: flex;
+                align-items: center;
+                justify-content: space-between;
+                height: 60px;
+                max-width: 1120px;
+            }
+
+            .site-logo {
+                display: flex;
+                align-items: center;
+                flex-shrink: 0;
+            }
+            .site-logo:hover {
+                text-decoration: none;
+            }
+            .site-logo-img {
+                display: block;
+                height: 34px;
+                width: auto;
+            }
+
+            .nav-home-link {
+                padding: 6px 14px;
+                border-radius: var(--radius);
+                color: var(--text-muted);
+                font-size: 13px;
+                font-weight: 500;
+                text-decoration: none;
+                transition: color 0.15s, background 0.15s;
+            }
+            .nav-home-link:hover {
+                color: var(--text);
+                background: var(--bg-hover);
+                text-decoration: none;
+            }
+
+            /* ── Error Card ────────────────────────────────────────── */
+            .error-section {
+                flex: 1;
+                display: flex;
+                align-items: center;
+                justify-content: center;
+                padding: 100px 24px 60px;
+            }
+
+            .error-card {
+                background: var(--bg-card);
+                border: 1px solid var(--border);
+                border-radius: var(--radius-card);
+                padding: 48px 40px;
+                text-align: center;
+                box-shadow: var(--shadow);
+                width: 100%;
+            }
+
+            .error-icon {
+                width: 56px;
+                height: 56px;
+                margin: 0 auto 20px;
+                border-radius: 50%;
+                background: var(--danger-dim);
+                border: 1px solid var(--danger);
+                display: flex;
+                align-items: center;
+                justify-content: center;
+                color: var(--danger);
+                font-size: 26px;
+                font-weight: 700;
+                line-height: 1;
+            }
+
+            .error-card h1 {
+                font-size: 1.4rem;
+                font-weight: 700;
+                letter-spacing: -0.02em;
+                color: var(--text);
+                margin-bottom: 16px;
+                line-height: 1.3;
+            }
+
+            .error-card p {
+                color: var(--text-muted);
+                font-size: 14px;
+                line-height: 1.7;
+                margin-bottom: 12px;
+            }
+
+            .error-card p strong {
+                color: var(--text);
+            }
+
+            .error-card .highlight {
+                color: var(--accent);
+            }
+
+            .error-card .code-sample {
+                display: inline-block;
+                background: var(--bg-inner);
+                border: 1px solid var(--border);
+                border-radius: 4px;
+                padding: 3px 10px;
+                font-size: 13px;
+                color: var(--accent);
+                margin: 4px 2px;
+            }
+
+            .divider {
+                height: 1px;
+                background: var(--border);
+                margin: 28px 0;
+                opacity: 0.5;
+            }
+
+            .btn {
+                display: inline-flex;
+                align-items: center;
+                gap: 8px;
+                padding: 12px 28px;
+                border-radius: var(--radius);
+                border: none;
+                cursor: pointer;
+                font-size: 14px;
+                font-weight: 600;
+                white-space: nowrap;
+                text-decoration: none;
+                transition:
+                    opacity 0.15s,
+                    background 0.15s,
+                    transform 0.1s;
+            }
+            .btn:hover {
+                opacity: 0.85;
+                text-decoration: none;
+            }
+            .btn:active {
+                transform: scale(0.97);
+            }
+
+            .btn-primary {
+                background: transparent;
+                color: #fff;
+                border: 1px solid var(--accent);
+                box-shadow:
+                    0 0 8px rgba(0, 245, 255, 0.35),
+                    inset 0 0 8px rgba(0, 245, 255, 0.04);
+            }
+            .btn-primary:hover {
+                background: rgba(0, 245, 255, 0.08);
+                box-shadow:
+                    0 0 14px rgba(0, 245, 255, 0.5),
+                    inset 0 0 10px rgba(0, 245, 255, 0.06);
+            }
+
+            .btn-ghost {
+                background: var(--bg-hover);
+                color: var(--text);
+                border: 1px solid var(--border);
+            }
+            .btn-ghost:hover {
+                opacity: 0.85;
+                background: var(--bg-hover);
+                border-color: var(--border);
+            }
+
+            .btn-block {
+                width: 100%;
+                justify-content: center;
+            }
+
+            .btn-group {
+                display: flex;
+                flex-direction: column;
+                gap: 10px;
+                margin-top: 4px;
+            }
+
+            /* ── Mobile ────────────────────────────────────────────── */
+            @media (max-width: 600px) {
+                .error-card {
+                    padding: 36px 24px;
+                }
+                .error-card h1 {
+                    font-size: 1.2rem;
+                }
+            }
+        </style>
+    </head>
+    <body>
+        <!-- ═══════════════════════════════════════════════════════════════
+         HEADER
+         ═══════════════════════════════════════════════════════════════ -->
+        <header class="site-header">
+            <div class="container">
+                <a href="/" class="site-logo">
+                    <img
+                        src="assets/images/logo.svg"
+                        alt="Derez.ai"
+                        width="132"
+                        height="34"
+                        class="site-logo-img"
+                    />
+                </a>
+                <a href="/#pricing" class="nav-home-link">Back to Pricing &rarr;</a>
+            </div>
+        </header>
+
+        <!-- ═══════════════════════════════════════════════════════════════
+         ERROR CARD
+         ═══════════════════════════════════════════════════════════════ -->
+        <section class="error-section">
+            <div class="container">
+                <div class="error-card">
+                    <div class="error-icon">!</div>
+
+                    <h1>This coupon has already been used</h1>
+
+                    <p>
+                        Coupon codes and discount keys on Derez.ai are
+                        <strong>single-use only</strong>.
+                        Each code can be applied to exactly one purchase.
+                    </p>
+
+                    <p>
+                        If you&rsquo;ve already used this code, the discount
+                        was applied to your first order and cannot be
+                        reused.
+                    </p>
+
+                    <div class="divider"></div>
+
+                    <p>
+                        You can still buy your agent at the regular price
+                        &mdash; no coupon code needed. Just head over to
+                        the <span class="highlight">pricing section</span>,
+                        pick your plan, and check out with Stripe.
+                    </p>
+
+                    <div class="btn-group">
+                        <a href="/#pricing" class="btn btn-primary btn-block">
+                            Go to Pricing &amp; Buy
+                        </a>
+                        <a href="/" class="btn btn-ghost btn-block">
+                            Back to Homepage
+                        </a>
+                    </div>
+                </div>
+            </div>
+        </section>
+    </body>
+</html>
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