404 Not Found Page

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f8fafc;
  min-height: 100vh;
  color: #111;
}

.page {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 40px;
  max-width: 1100px;
  margin: 0 auto;
  width: 100%;
}

.logo {
  font-size: 20px;
  font-weight: 800;
  color: #111;
  text-decoration: none;
}

.nav-home {
  font-size: 14px;
  color: #6366f1;
  text-decoration: none;
  font-weight: 600;
}

.content {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px 24px 80px;
  text-align: center;
  gap: 20px;
}

/* Glitch effect */
.glitch-wrap {
  height: 120px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.glitch {
  font-size: clamp(80px, 18vw, 120px);
  font-weight: 900;
  color: #111;
  position: relative;
  letter-spacing: -4px;
}

.glitch::before,
.glitch::after {
  content: attr(data-text);
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.glitch::before {
  color: #6366f1;
  animation: glitch-1 2.5s infinite;
  clip-path: polygon(0 0, 100% 0, 100% 45%, 0 45%);
}

.glitch::after {
  color: #ef4444;
  animation: glitch-2 2.5s infinite;
  clip-path: polygon(0 55%, 100% 55%, 100% 100%, 0 100%);
}

@keyframes glitch-1 {
  0%,
  90%,
  100% {
    transform: translate(0);
    opacity: 0;
  }
  92% {
    transform: translate(-3px, 2px);
    opacity: 0.8;
  }
  94% {
    transform: translate(3px, -2px);
    opacity: 0.8;
  }
  96% {
    transform: translate(0);
    opacity: 0;
  }
}

@keyframes glitch-2 {
  0%,
  90%,
  100% {
    transform: translate(0);
    opacity: 0;
  }
  93% {
    transform: translate(3px, 1px);
    opacity: 0.8;
  }
  95% {
    transform: translate(-3px, -1px);
    opacity: 0.8;
  }
  97% {
    transform: translate(0);
    opacity: 0;
  }
}

/* Illustration */
.illustration {
  animation: float 4s ease-in-out infinite;
}

.illustration svg {
  width: 200px;
  height: auto;
}

@keyframes float {
  0%,
  100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-12px);
  }
}

h1 {
  font-size: clamp(22px, 4vw, 30px);
  font-weight: 700;
  color: #111;
}

p {
  font-size: 16px;
  color: #666;
  max-width: 420px;
  line-height: 1.6;
}

/* Search */
.search-box {
  display: flex;
  align-items: center;
  gap: 0;
  background: #fff;
  border: 1.5px solid #e5e7eb;
  border-radius: 12px;
  padding: 4px 4px 4px 16px;
  width: 100%;
  max-width: 400px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

.search-box svg {
  width: 16px;
  height: 16px;
  color: #9ca3af;
  flex-shrink: 0;
}

.search-box input {
  flex: 1;
  border: none;
  outline: none;
  padding: 8px 12px;
  font-size: 14px;
  background: none;
  color: #111;
}

.search-box button {
  padding: 9px 18px;
  background: #6366f1;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: opacity 0.15s;
}

.search-box button:active {
  opacity: 0.85;
}

/* Quick links */
.quick-links {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  justify-content: center;
  font-size: 14px;
}

.quick-links span {
  color: #999;
}

.quick-links a {
  color: #6366f1;
  text-decoration: none;
  font-weight: 500;
  padding: 4px 12px;
  background: #eef2ff;
  border-radius: 20px;
  transition: background 0.15s;
}

.quick-links a:hover {
  background: #e0e7ff;
}

const form = document.querySelector(".search-box");
if (form) {
  const btn = form.querySelector("button");
  const input = form.querySelector("input");
  btn.addEventListener("click", () => {
    if (input.value.trim()) {
      // In a real app: window.location = `/search?q=${encodeURIComponent(input.value)}`
      input.value = "";
      input.focus();
    }
  });
  input.addEventListener("keydown", (e) => {
    if (e.key === "Enter") btn.click();
  });
}

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="style.css" />
    <title>404 — Page Not Found</title>
  </head>
  <body>
    <div class="page">
      <nav class="nav">
        <a href="#" class="logo">Brand</a>
        <a href="#" class="nav-home">Go to homepage</a>
      </nav>

      <main class="content">
        <div class="glitch-wrap" aria-hidden="true">
          <span class="glitch" data-text="404">404</span>
        </div>

        <div class="illustration">
          <svg viewBox="0 0 200 140" fill="none" xmlns="http://www.w3.org/2000/svg">
            <ellipse cx="100" cy="120" rx="80" ry="10" fill="#e5e7eb"/>
            <rect x="60" y="30" width="80" height="70" rx="6" fill="#f3f4f6" stroke="#d1d5db" stroke-width="2"/>
            <rect x="70" y="42" width="60" height="6" rx="3" fill="#d1d5db"/>
            <rect x="70" y="54" width="40" height="6" rx="3" fill="#e5e7eb"/>
            <rect x="70" y="66" width="50" height="6" rx="3" fill="#e5e7eb"/>
            <circle cx="155" cy="40" r="22" fill="#fef2f2" stroke="#fca5a5" stroke-width="2"/>
            <text x="149" y="47" font-size="22" fill="#ef4444">✕</text>
            <circle cx="100" cy="100" r="12" fill="#fff" stroke="#d1d5db" stroke-width="2"/>
            <text x="95" y="105" font-size="12" fill="#9ca3af">?</text>
          </svg>
        </div>

        <h1>Page not found</h1>
        <p>The page you're looking for doesn't exist or has been moved. Let's get you back on track.</p>

        <div class="search-box">
          <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="11" cy="11" r="8"/><line x1="21" y1="21" x2="16.65" y2="16.65"/></svg>
          <input type="text" placeholder="Search for something…" />
          <button>Search</button>
        </div>

        <div class="quick-links">
          <span>Or try:</span>
          <a href="#">Home</a>
          <a href="#">Blog</a>
          <a href="#">Docs</a>
          <a href="#">Support</a>
        </div>
      </main>
    </div>
    <script src="script.js"></script>
  </body>
</html>