:root {
  --bg-main: #0b0f14;
  --bg-alt: #111722;
  --text-main: #e6e9ee;
  --text-muted: #9aa3ad;
  --accent: #ff6b00;
}

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

body {
  font-family: Inter, system-ui, sans-serif;
  background-color: var(--bg-main);
  color: var(--text-main);
  line-height: 1.6;
}

/* HEADER */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(11,15,20,0.9);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid rgba(255,255,255,0.05);
}

.header-inner {
  max-width: 1200px;
  margin: auto;
  padding: 1rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title a {
  color: var(--text-main);
  text-decoration: none;
  font-weight: 600;
  letter-spacing: 0.5px;
}

.main-nav a {
  margin-left: 1.5rem;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.95rem;
}

.main-nav a.active,
.main-nav a:hover {
  color: var(--accent);
}

/*===   AÑADIDO PARA EL MENU DESPLEGABLE ===*/
/* DROPDOWN CLICK-BASED */

.nav-dropdown {
  position: relative;
  display: inline-block;
  margin-left: 1.5rem;
}

.nav-toggle {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.95rem;
  cursor: pointer;
  padding: 0;
}

.nav-toggle.active {
  color: var(--accent);
}

.dropdown-content {
  display: none;
  position: absolute;
  top: 1.8rem;
  left: 0;
  background: var(--bg-alt);
  border-radius: 6px;
  min-width: 180px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.4);
  z-index: 999;
}

.dropdown-content a {
  display: block;
  padding: 0.6rem 1rem;
  color: var(--text-main);
  text-decoration: none;
  font-size: 0.9rem;
}

.dropdown-content a.active {
  color: var(--accent);
}

.dropdown-content a:hover {
  background: rgba(255,255,255,0.05);
}

/* Visible when open */
.nav-dropdown.open .dropdown-content {
  display: block;
}

/* HERO */
.hero {
  min-height: 60vh;
  display: flex;
  align-items: center;
  background: linear-gradient(
    rgba(11,15,20,0.85),
    rgba(11,15,20,0.95)
  ),
  url("../imagenes/hero-usadesign.jpg") center / cover no-repeat;
}

.hero-content {
  max-width: 800px;
  margin: auto;
  padding: 3rem 1.5rem;
  text-align: center;
}

.hero h1 {
  font-size: clamp(2.2rem, 4vw, 3.5rem);
  margin-bottom: 1rem;
}

.hero-subtitle {
  color: var(--text-muted);
  font-size: 1.1rem;
}

/* SECTIONS */
section {
  max-width: 1000px;
  margin: auto;
  padding: 4rem 1.5rem;
}

.intro p {
  font-size: 1.05rem;
}

/* CHAPTER GRID */
.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.chapter-card {
  background: var(--bg-alt);
  padding: 1.5rem;
  border-radius: 8px;
  text-decoration: none;
  color: var(--text-main);
  transition: transform 0.2s ease, background 0.2s ease;
}

.chapter-card:hover {
  transform: translateY(-4px);
  background: #151c2b;
}

.chapter-card h3 {
  color: var(--accent);
  margin-bottom: 0.5rem;
}

/* CTA QUIZ */
.cta-quiz {
  text-align: center;
  background: var(--bg-alt);
  border-radius: 12px;
}

.btn-primary {
  display: inline-block;
  margin-top: 1.5rem;
  padding: 0.75rem 1.75rem;
  background: var(--accent);
  color: #000;
  text-decoration: none;
  font-weight: 600;
  border-radius: 25px;
}





















/* FOOTER */
.site-footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.85rem;
}