body {
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #000;
    color: #fff;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    text-align: center;
    flex-direction: column;
}

.container {
    padding: 20px;
}

.heartbeat {
    width: 80%;
    max-width: 600px;
    margin: 30px auto;
}

button {
    background-color: #111;
    color: #fff;
    border: 2px solid #00FF00;
    padding: 10px 20px;
    font-size: 18px;
    cursor: pointer;
    border-radius: 8px;
    margin-bottom: 20px;
}

button:hover {
    background-color: #00FF00;
    color: #000;
}

.pista {
    font-size: 18px;
    line-height: 1.6;
}