body {
  font-family: Arial, sans-serif;
  background: #f4f4f4;
  margin: 0;
  padding: 0;
}
.container {
  max-width: 800px;
  margin: auto;
  background: #fff;
  padding: 20px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}
input, button {
  padding: 10px;
  margin: 5px 0;
  width: 100%;
  box-sizing: border-box;
}
button {
  cursor: pointer;
}