*{
    margin:0;
    padding:0;
    box-sizing:border-box;
    font-family:Arial, Helvetica, sans-serif;
}

body{
    background:linear-gradient(135deg,#1e3c72,#2a5298);
    height:100vh;
    display:flex;
    justify-content:center;
    align-items:center;
}

.contenedor{
    width:100%;
    display:flex;
    justify-content:center;
}

.caja{
    background:#fff;
    width:380px;
    padding:35px;
    border-radius:15px;
    box-shadow:0 10px 25px rgba(0,0,0,0.3);
    text-align:center;
}

.caja h2{
    color:#1e3c72;
    margin-bottom:10px;
}

.caja p{
    color:gray;
    margin-bottom:20px;
}

.grupo{
    text-align:left;
    margin-bottom:15px;
}

.grupo label{
    font-weight:bold;
    display:block;
    margin-bottom:5px;
}

.grupo input{
    width:100%;
    padding:12px;
    border:1px solid #ccc;
    border-radius:8px;
    outline:none;
}

.grupo input:focus{
    border-color:#2a5298;
}

.btn{
    width:100%;
    padding:12px;
    border:none;
    background:#28a745;
    color:white;
    font-size:16px;
    border-radius:8px;
    cursor:pointer;
    transition:.3s;
}

.btn:hover{
    background:#218838;
}

.volver{
    display:block;
    margin-top:12px;
    text-decoration:none;
    background:#007bff;
    color:white;
    padding:12px;
    border-radius:8px;
}

.volver:hover{
    background:#0056b3;
}

.correcto{
    background:#d4edda;
    color:#155724;
    padding:10px;
    border-radius:8px;
    margin-bottom:15px;
}

.error{
    background:#f8d7da;
    color:#721c24;
    padding:10px;
    border-radius:8px;
    margin-bottom:15px;
}