/* ===============================
   VARIABLES
=============================== */
:root {
  --font-primary: 'Poppins', sans-serif;
  --color-bg-gradient-start: #f9fafc;
  --color-bg-gradient-end: #f0f2f5;
  --color-primary: #1f3b2c;
  --color-secondary: #2c5545;
  --color-accent: #c0aa83;
  --color-text: #1c1b18;
  --color-card-border: #ddd;
  --color-card-shadow: rgba(0, 0, 0, 0.08);
  --color-footer-bg: #1f3b2c;
  --color-footer-text: #f5f5f5;
  --scroll-btn-bg: var(--color-secondary);
  --scroll-btn-color: white;
  --scroll-btn-size: 45px;
  --scroll-btn-radius: 50%;
  --scroll-btn-shadow: 0 4px 10px rgba(0,0,0,0.3);
}

/* ===============================
   GLOBAL STYLES
=============================== */
body {
  font-family: var(--font-primary);
  background: linear-gradient(135deg, var(--color-bg-gradient-start), var(--color-bg-gradient-end));
  color: var(--color-text);
  margin: 0;
  line-height: 1.6;
  scroll-behavior: smooth;
}

/* ===============================
   NAVBAR
=============================== */
.navbar {
  background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.1);
}

.navbar-brand {
  font-weight: 600;
  letter-spacing: 1px;
}

.nav-link {
  font-weight: 500;
  transition: color 0.3s;
}

.nav-link:hover {
  color: var(--color-accent) !important;
}

/* ===============================
   HERO SECTION
=============================== */
.hero {
  background: url('https://images.unsplash.com/photo-1529101091764-c3526daf38fe?ixlib=rb-4.0.3&q=80&auto=format&fit=crop&w=1950') no-repeat center/cover;
  min-height: 60vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  position: relative;
  color: white;
}

.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background: rgba(31, 59, 44, 0.6);
}

.hero-content {
  position: relative;
  z-index: 1;
  backdrop-filter: blur(8px);
  padding: 30px 20px;
  border-radius: 15px;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 700;
  margin-bottom: 10px;
}

.hero p {
  font-size: 1.2rem;
  opacity: 0.9;
}

/* ===============================
   CARD LAYOUT
=============================== */
.card-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 300px));
  justify-content: start;
  gap: 20px;
  margin-top: 20px;
}

.material-card {
  background: #fff;
  border: 1px solid var(--color-card-border);
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 2px 8px var(--color-card-shadow);
  transition: all 0.3s ease;
  text-align: center;
}

.material-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.15);
}

.material-card h3 {
  margin: 0 0 8px;
  font-size: 1.2rem;
  color: var(--color-primary);
}

.material-card p {
  font-size: 0.95rem;
  margin-bottom: 12px;
  color: #333;
}

.btn-download {
  border-radius: 50px;
  padding: 10px 18px;
  font-weight: 500;
  transition: all 0.3s ease;
  border: 1px solid var(--color-secondary);
  color: var(--color-secondary);
  background: transparent;
}

.btn-download:hover {
  background: var(--color-secondary);
  color: white;
  border-color: var(--color-secondary);
}

/* ===============================
   SECTION TITLES
=============================== */
section h2 {
  margin-top: 50px;
  font-weight: 600;
  color: var(--color-secondary);
  border-bottom: 2px solid #ddd;
  padding-bottom: 10px;
}

/* ===============================
   FOOTER
=============================== */
footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: 20px;
  text-align: center;
  font-size: 0.9rem;
}

/* ===============================
   SCROLL TO TOP BUTTON
=============================== */
#scrollTopBtn {
  display: none;
  position: fixed;
  bottom: 30px;
  right: 30px;
  z-index: 999;
  width: var(--scroll-btn-size);
  height: var(--scroll-btn-size);
  background-color: var(--scroll-btn-bg);
  color: var(--scroll-btn-color);
  border: none;
  border-radius: var(--scroll-btn-radius);
  box-shadow: var(--scroll-btn-shadow);
  cursor: pointer;
  font-size: 24px;
  align-items: center;
  justify-content: center;
  display: flex;
  transition: all 0.3s ease;
}

#scrollTopBtn:hover {
  background-color: var(--color-primary);
}

/* ===============================
   RESPONSIVE
=============================== */
@media (max-width: 992px) {
  .hero h1 {
    font-size: 2.5rem;
  }
  .hero p {
    font-size: 1.1rem;
  }
}

@media (max-width: 768px) {
  .hero {
    min-height: 50vh;
  }
  .hero h1 {
    font-size: 2rem;
  }
  .hero p {
    font-size: 1rem;
  }

  .card-container {
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    justify-content: start;
  }

  #scrollTopBtn {
    width: 40px;
    height: 40px;
    font-size: 20px;
  }
}

@media (max-width: 480px) {
  .card-container {
    grid-template-columns: 1fr;
  }
}