:root {
  --primary: #0072ff;
  --secondary: #004d99;
  --text: #2c3e50;
  --text-light: #555;
  --bg: #f7f9fc;
  --card-bg: #fff;
  --shadow: 0 6px 20px rgba(0, 0, 0, 0.08);
  --shadow-hover: 0 15px 35px rgba(0, 0, 0, 0.18);
  --radius: 12px;
  --transition: 0.3s ease;
}

body.dark {
  --bg: #1e1e1e;
  --card-bg: #2b2b2b;
  --text: #e2e2e2;
  --text-light: #ccc;
  --primary: #0072ff;
  --secondary: #0056cc;
  --shadow: 0 6px 20px rgba(0, 0, 0, 0.6);
  --shadow-hover: 0 15px 35px rgba(0, 0, 0, 0.7);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Poppins', sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  transition: background 0.4s ease, color 0.4s ease;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

a {
  text-decoration: none;
  color: var(--primary);
  transition: var(--transition);
}

a:hover,
a:focus {
  color: var(--secondary);
}

header {
  position: fixed;
  top: 0;
  width: 100%;
  background: var(--card-bg);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.1);
  z-index: 3000;
  transition: background var(--transition), color var(--transition);
}

body.dark header {
  background: var(--card-bg);
}

header.scrolled {
  background: var(--primary);
}

header.scrolled .logo,
header.scrolled nav a {
  color: #fff;
}

header.scrolled nav a.active::after {
  background: #fff;
}

.container {
  max-width: 1200px;
  margin: auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.logo {
  font-size: 1.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--primary);
  transition: color var(--transition);
}

.theme-toggle {
  position: relative;
  z-index: 5000;
  background: none;
  border: none;
  cursor: pointer;
  margin-right: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.3s ease;
}

.theme-toggle:hover {
  transform: scale(1.1);
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  font-size: 1.5rem;
  transition: all 0.3s ease;
  display: inline-block;
}

body:not(.dark) .theme-toggle .icon-sun {
  display: none;
}

body:not(.dark) .theme-toggle .icon-moon {
  display: inline;
  color: var(--text);
}

body.dark .theme-toggle .icon-sun {
  display: inline;
  color: #fff;
}

body.dark .theme-toggle .icon-moon {
  display: none;
}

header.scrolled .theme-toggle .icon-sun,
header.scrolled .theme-toggle .icon-moon {
  color: #fff;
}

nav {
  display: flex;
  gap: 20px;
  transition: var(--transition);
}

nav a {
  font-weight: 500;
  font-size: 0.95rem;
  position: relative;
  color: var(--text);
  transition: color var(--transition);
}

body.dark nav a {
  color: #e2e2e2;
}

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

body.dark nav a::after {
  background: var(--primary);
}

nav a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary);
  transition: width var(--transition);
}

nav a:hover::after,
nav a.active::after {
  width: 100%;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  position: relative;
  z-index: 5000;
}

.nav-toggle span {
  width: 25px;
  height: 3px;
  background: var(--text);
  transition: var(--transition);
}

header.scrolled .nav-toggle span {
    background: #fff;
}

body.dark .nav-toggle span {
  background: var(--text);
}

main {
  padding-top: 70px;
  max-width: 1200px;
  margin: auto;
  padding-left: 20px;
  padding-right: 20px;
  flex-grow: 1;
}

section {
  padding: 80px 0;
  opacity: 0;
  transform: translateY(30px);
  transition: all 0.6s ease-in-out;
}

section.visible {
  opacity: 1;
  transform: translateY(0);
}

section:nth-child(even) {
  background: #e9ecef;
}

body.dark section:nth-child(even) {
  background: #222;
}

h1 {
  font-size: 3.5rem;
  text-align: center;
  color: #fff;
  margin-bottom: 20px;
  font-weight: 700;
}

h2 {
  font-size: 2.6rem;
  text-align: center;
  color: var(--secondary);
  margin-bottom: 40px;
  font-weight: 600;
}

h3 {
  font-size: 1.3rem;
  color: var(--primary);
  margin-bottom: 10px;
  font-weight: 600;
}

p {
  color: var(--text-light);
  font-size: 1.1rem;
  line-height: 1.6;
  text-align: center;
}

.hero-card {
  min-height: 90vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--bg);
  padding: 120px 20px 40px;
  transition: background 0.4s ease;
}

.hero-content {
  max-width: 1000px;
  width: 90%;
  text-align: center;
  padding: 60px;
  border-radius: 20px;
  background: linear-gradient(135deg, #0072ff 0%, #004d99 100%);
  backdrop-filter: blur(10px);
  border: 2px solid rgba(255, 255, 255, 0.15);
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
  color: #fff;
  transition: transform 0.4s ease, box-shadow 0.4s ease;
}

.hero-content:hover {
  transform: translateY(-10px) scale(1.02);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.35);
}

.hero-content p {
  font-size: 1.3rem;
  margin-bottom: 25px;
  color: #f0f0f0;
}

.btn-hero {
  display: inline-block;
  padding: 15px 40px;
  border-radius: 50px;
  font-weight: 700;
  background: #fff;
  color: #0072ff;
  text-decoration: none;
  transition: all 0.3s ease;
}

.btn-hero:hover {
  background: #cce4ff;
  box-shadow: 0 8px 25px rgba(0, 114, 255, 0.4);
}

.grid-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 30px;
  max-width: 1100px;
  margin: 0 auto;
}

.card {
  background: var(--card-bg);
  padding: 30px 25px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
  transition: transform 0.4s ease, box-shadow 0.4s ease;
  min-height: 250px;
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-hover);
}

.card i {
  font-size: 2.2rem;
  margin-bottom: 15px;
  color: var(--secondary);
}

.card p {
  color: var(--text-light);
  font-size: 1rem;
  text-align: justify;
  flex-grow: 1;
}

.reference-card {
  min-height: 280px;
  justify-content: space-between;
}

.reference-card p {
  margin-bottom: 20px;
  font-size: 0.95rem;
}

.btn-card {
  display: block;
  width: 100%;
  padding: 10px 15px;
  font-weight: 600;
  font-size: 0.95rem;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 50px;
  cursor: pointer;
  transition: all 0.3s ease;
  margin-top: auto;
}

.btn-card:hover {
  background: var(--secondary);
  color: #fff;
  transform: scale(1.02);
  box-shadow: 0 4px 15px rgba(0, 77, 153, 0.4);
}

.site-footer {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  text-align: center;
  font-size: 0.95rem;
  font-weight: 500;
  padding: 25px 10px;
  border-top: 3px solid rgba(255, 255, 255, 0.25);
  box-shadow: 0 -2px 8px rgba(0, 0, 0, 0.15);
}

@media (max-width: 1100px) {
  .grid-cards {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  }

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

@media (max-width: 992px) {
  nav a {
    font-size: 0.85rem;
  }

  nav {
    gap: 15px;
  }
}

@media (max-width: 850px) {
  nav {
    display: none;
    position: absolute;
    top: 70px;
    left: 0;
    width: 100%;
    flex-direction: column;
    gap: 0;
    background: var(--card-bg);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.15);
    z-index: 2999;
    padding: 10px 0;
  }

  header.scrolled nav a {
    color: var(--text);
  }

  nav.active {
    display: flex;
  }

  nav a {
    width: 100%;
    padding: 12px 20px;
    margin-left: 0;
    text-align: left;
    border-bottom: 1px solid rgba(0, 0, 0, 0.15);
    color: var(--text);
  }

  nav a:hover,
  nav a.active {
    color: var(--secondary);
    background: rgba(0, 114, 255, 0.05);
  }

  body.dark nav a {
    color: var(--text);
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
  }

  body.dark nav a:hover,
  body.dark nav a.active {
    background: rgba(255, 255, 255, 0.1);
  }

  nav a:last-child {
    border-bottom: none;
  }

  nav a::after {
    content: none;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-toggle span {
    background: var(--text);
  }

  body.dark .nav-toggle span {
    background: var(--text);
  }

  .grid-cards {
    grid-template-columns: 1fr;
    max-width: 500px;
  }
}

@media (max-width: 600px) {
  .container {
    padding: 0 15px;
    height: 60px;
  }

  .logo {
    font-size: 1.4rem;
  }

  main {
    padding-top: 60px;
  }

  .hero-card {
    padding: 80px 15px 40px;
  }

  .hero-content {
    padding: 30px 20px;
  }

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

  .hero-content p {
    font-size: 1rem;
  }

  .card p {
    text-align: left;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 2.2rem;
  }

  h2 {
    font-size: 1.8rem;
  }
}