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

body{
    font-family:Arial, Helvetica, sans-serif;
    background:#111;
    color:#fff;
    line-height:1.6;
}

.container{
    width:90%;
    max-width:1200px;
    margin:auto;
}

header{
    background:#111;
    border-bottom:1px solid #222;
    padding:20px 0;
    position:sticky;
    top:0;
    z-index:1000;
}

header .container{
    display:flex;
    justify-content:space-between;
    align-items:center;
}

.logo{
    width:300px;
    max-width:100%;
}

nav a{
    color:#fff;
    text-decoration:none;
    margin-left:25px;
    font-weight:bold;
    transition:0.3s;
}

nav a:hover{
    color:#e53935;
}

.hero{
    text-align:center;
    padding:80px 20px;
}

.hero .logo{
    width:450px;
    max-width:100%;
    margin-bottom:25px;
}

.hero h1{
    font-size:3rem;
    margin-bottom:10px;
}

.hero h2{
    color:#e53935;
    margin-bottom:25px;
    font-size:1.8rem;
}

.hero p{
    max-width:900px;
    margin:15px auto;
    color:#ccc;
    font-size:1.1rem;
}

.btn{
    display:inline-block;
    margin-top:25px;
    padding:15px 35px;
    background:#e53935;
    color:#fff;
    text-decoration:none;
    border-radius:8px;
    font-weight:bold;
}

.btn:hover{
    background:#c62828;
}

.section{
    padding:80px 20px;
    text-align:center;
}

.section h2{
    margin-bottom:40px;
    color:#e53935;
    font-size:2.2rem;
}

.cards{
    display:grid;
    grid-template-columns:repeat(auto-fit,minmax(280px,1fr));
    gap:25px;
    margin-top:30px;
}

.card{
    background:#1b1b1b;
    border:1px solid #333;
    border-radius:12px;
    padding:30px;
}

.card h3{
    margin-bottom:15px;
    color:#e53935;
}

.card p{
    color:#ddd;
}

.btn-card{
    display:inline-block;
    margin-top:20px;
    padding:12px 25px;
    background:#e53935;
    color:#fff;
    text-decoration:none;
    border-radius:6px;
}

.btn-card:hover{
    background:#c62828;
}

.dark{
    background:#181818;
}

.dark ul{
    max-width:700px;
    margin:20px auto;
    text-align:left;
}

.dark li{
    margin-bottom:12px;
    color:#fff;
}

form{
    max-width:700px;
    margin:auto;
}

form input,
form select{
    width:100%;
    padding:15px;
    margin-bottom:15px;
    border:none;
    border-radius:6px;
}

form button{
    width:100%;
    padding:15px;
    border:none;
    background:#e53935;
    color:#fff;
    border-radius:6px;
    cursor:pointer;
    font-size:16px;
}

form button:hover{
    background:#c62828;
}

.nota{
    margin-top:20px;
    color:#ccc;
}

#contacto{
    background:#000;
    color:#fff;
}

#contacto h2{
    color:#e53935;
    margin-bottom:30px;
}

#contacto p{
    color:#fff;
    font-size:22px;
    margin-bottom:15px;
}

footer{
    background:#000;
    color:#ccc;
    text-align:center;
    padding:30px;
    border-top:1px solid #222;
}

footer p{
    margin-bottom:10px;
}

@media(max-width:768px){

    header .container{
        flex-direction:column;
    }

    nav{
        margin-top:20px;
    }

    nav a{
        display:block;
        margin:10px 0;
    }

    .hero h1{
        font-size:2rem;
    }

    .hero h2{
        font-size:1.3rem;
    }

    .hero .logo{
        width:280px;
    }
}
```