style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    user-select: none;
}

body{
    font-family: Arial, Helvetica, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f8f8f8;
}

.input-box{
    width: 450px;
}

.input-box h2{
    font-size: 2.5rem;
    text-transform: uppercase;
}

.input-box input{
    position: relative;
    height: 60px;
    width: 100%;
    background: transparent;
    border: none;
    border-radius: 8px;
    color: #333;
    margin: 15px 0 20px;
    outline: none;
    font-size: 24px;
    padding: 0 20px;
    letter-spacing: 2px;
    box-shadow: -4px -4px 5px rgba(255, 255, 255, 1),
      inset 4px 4px 5px rgba(0, 0, 0, 0.2),
      inset -4px -4px 10px rgba(255, 255, 255, 1),
      4px 4px 5px rgba(0, 0, 0, 0.1);
}

.input-box input::placeholder {
    letter-spacing: 0;
  }

  .input-box #btn {
    position: relative;
    background: #333;
    color: #fff;
    cursor: pointer;
    font-size: 24px;
    display: inline-block;
    padding: 10px 15px;
    border-radius: 8px;
  }

  .input-box #btn:active {
    background: #9c27b0;
  }