*{margin:0;padding:0;box-sizing:border-box}
body{
  font-family:Arial,Helvetica,sans-serif;
  background:#f4f4f4;
  color:#333;
}

/* Header */
header{background:#111;padding:15px 20px}
.navbar{
  max-width:1200px;
  margin:auto;
  display:flex;
  align-items:center;
  justify-content:space-between;
}
.logo{
  color:#fff;
  font-size:22px;
  text-decoration:none;
}

/* Error Section */
.error-container{
  max-width:800px;
  margin:80px auto;
  padding:0 20px;
  text-align:center;
}
.error-code{
  font-size:96px;
  font-weight:bold;
  color:#111;
}
.error-title{
  font-size:28px;
  margin:10px 0;
}
.error-text{
  font-size:16px;
  color:#555;
  line-height:1.6;
  margin-bottom:30px;
}

/* Buttons */
.error-actions a{
  display:inline-block;
  margin:10px;
  padding:12px 26px;
  background:#111;
  color:#fff;
  text-decoration:none;
  border-radius:4px;
  font-weight:600;
  transition:background .2s ease, transform .2s ease;
}
.error-actions a:hover{
  background:#333;
  transform:translateY(-2px);
}

/* Footer */
footer{
  background:#111;
  color:#ccc;
  text-align:center;
  padding:15px;
  margin-top:80px;
}

/* Mobile */
@media(max-width:600px){
  .error-code{font-size:72px}
  .error-title{font-size:22px}
}