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

<style>
    body{
    margin:0;
    font-family: 'Segoe UI', sans-serif;
    background:#f4f9f4;
}
    .topnav{
        overflow: hidden;
        background-color: #FFF8E1;
    }

    .topnav a{
        float: left;
        display: block;
        color: #4E342E;
        text-align: center;
        padding: 14px 16px;
        text-decoration: none;
        font-size: 17px;
    }

    .topnav a:hover{
        background-color: #D6EAF8;
        color: black;
    }

    .topnav a.active{
        background-color: #FFF8E1;
        color: black;
    }

    .topnav .icon{
        display: none;
    }

    
    
    @media screen and (max-width: 600px) {
        .topnav a:not(:first-child) {
            display: none;
        }
        .topnav a.icon{
            float: right;
            display: block;
        }
    }

    @media screen and (max-width: 600px) {
        .topnav.responsive {
            position: relative;
        }

        .topnav.responsive .icon{
            position: absolute;
            right: 0;
            top: 0;
        }

        .topnav.responsive a{
            float: none;
            display: block;
            text-align: left;
        }
    }
   </style>


body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background:#f4f9f4;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    width: 100%;
    margin: 80px auto;
    max-width: 500px;
}

h1 {
    text-align: center;
    margin-bottom: 1.5rem;
    color: #333;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: #555;
}

input {
    width: 100%;
    padding: 0.75rem;
    margin-bottom: 1.25rem;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

input:focus {
    outline: none;
    border-color: #4a90e2;
}

button {
    width: 100%;
    padding: 0.75rem;
    background: #4a90e2;
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: background 0.3s;
}

button:hover {
    background: #357abd;
}

button:disabled {
    background: #aaa;
    cursor: not-allowed;
}

#message {
    margin-top: 1rem;
    text-align: center;
    font-weight: 600;
}

.success {
    color: #28a745;
}

.error {
    color: #dc3545;
}