:root {
    --primary: #1a2b3c;    /* Azul Oscuro Principal */
    --secondary: #3498db;  /* Azul de Enlaces/Botones Secundarios */
    --accent: #27ae60;     /* Verde de Acción */
    --text-dark: #333;
    --text-light: #bdc3c7;
    --bg-light: #f4f7f9;
}

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

body {
    font-family: 'Inter', sans-serif;
    color: var(--text-dark);
    background-color: var(--bg-light);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 5%;
}

/* --- NAVBAR --- */
.navbar {
    background: var(--primary);
    padding: 1.2rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.logo {
    color: white;
    text-decoration: none;
    font-weight: 700;
    font-size: 1.4rem;
}

.menu-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 5px;
}

.menu-toggle span {
    width: 25px;
    height: 3px;
    background-color: white;
    border-radius: 2px;
}

.nav-links {
    display: flex;
    align-items: center;
}

.nav-links a {
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    margin-left: 25px;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.3s ease;
    padding-bottom: 5px;
    border-bottom: 2px solid transparent;
}

.nav-links a:hover {
    color: white;
}

/* Estado activo para links normales (Desktop) */
.nav-links a.active-link {
    color: white !important;
    border-bottom: 2px solid var(--secondary);
    opacity: 1;
}

/* Estilo base del botón de navegación */
.nav-links a.btn-nav {
    border-bottom: none;
    color: white;
    background: var(--secondary);
    padding: 10px 20px;
    border-radius: 5px;
}

.nav-links a.btn-nav:hover {
    background: #2980b9;
}

/* Resaltado especial para el botón de contacto cuando está activo */
.nav-links a.btn-nav.active-link {
    background: var(--accent); /* Cambia a verde para indicar ubicación */
    border-bottom: none;
}

/* --- HERO SECTION --- */
.hero {
    background: var(--primary);
    color: white;
    padding: 80px 0;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.hero-text h1 {
    font-size: 3rem;
    line-height: 1.1;
    margin-bottom: 25px;
}

.hero-text p {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 35px;
}

.btn-group { display: flex; gap: 20px; }

.btn {
    padding: 16px 32px;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 700;
    transition: all 0.3s ease;
    display: inline-block;
}

.btn-primary {
    background: var(--accent);
    color: white;
    box-shadow: 0 4px 15px rgba(39, 174, 96, 0.3);
}

.btn-secondary {
    background: rgba(255,255,255,0.1);
    color: white;
    border: 1px solid white;
}

.btn:hover { transform: translateY(-3px); opacity: 0.9; }

.hero-image img {
    width: 100%;
    max-width: 500px;
    display: block;
    margin: 0 auto;
    border-radius: 12px;
    box-shadow: 0 20px 50px rgba(0,0,0,0.4);
}

/* --- CHALLENGES & CARDS --- */
.challenges { padding: 80px 0; }

.section-title {
    text-align: center;
    font-size: 2.2rem;
    color: var(--primary);
    margin-bottom: 60px;
}

.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

.card {
    background: white;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.05);
    border-top: 6px solid var(--secondary);
    transition: 0.3s;
}

.card:hover { transform: translateY(-10px); }

.card h3 { margin-bottom: 15px; color: var(--primary); }

/* --- FOOTER --- */
.footer {
    text-align: center;
    padding: 50px;
    background: #eee;
    color: #7f8c8d;
}

/* --- MEDIA QUERIES (RESPONSIVE) --- */

@media (max-width: 900px) {
    .menu-toggle {
        display: flex;
    }

    .nav-links {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        width: 100%;
        background: var(--primary);
        padding: 20px 0;
        box-shadow: 0 10px 20px rgba(0,0,0,0.1);
    }

    .nav-links.active {
        display: flex;
    }

    .nav-links a {
        margin: 10px 5%;
        width: 90%;
        text-align: center;
        font-size: 1.1rem;
        border-bottom: none !important; 
    }

    /* Resaltado en móvil: Color de texto */
    .nav-links a.active-link {
        color: var(--secondary) !important;
        font-weight: 700;
    }

    .nav-links a.btn-nav {
        margin-top: 10px;
    }

    /* Hero móvil */
    .hero-grid { 
        grid-template-columns: 1fr; 
        text-align: center; 
        gap: 40px;
    }
    
    .hero-text h1 { font-size: 2.2rem; }
    
    .btn-group { 
        justify-content: center; 
        flex-direction: column;
    }

    .hero-image img {
        max-width: 80%;
    }
}