body {
  font-family: 'Inter', sans-serif;
  scroll-behavior: smooth;
}

.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.7);
  z-index: 1000;
  align-items: center;
  justify-content: center;
}

.modal-content {
  background: #ffffff;
  padding: 2rem;
  border-radius: 1rem;
  text-align: left;
  max-width: 90%;
  width: 600px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.2);
  max-height: 80vh;
  overflow-y: auto;
}

.modal-content h2 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: #1f2937;
}

.modal-content p {
  color: #4b5563;
  margin-bottom: 1rem;
}

.modal-content button {
  background: #0d9488;
  color: white;
  padding: 0.75rem 2rem;
  border-radius: 0.5rem;
  font-weight: 600;
  transition: all 0.3s ease;
  margin-top: 1rem;
  display: block;
  margin-left: auto;
}

.modal-content button:hover {
  background: #0b8276;
  transform: scale(1.05);
}

.nav-link {
  position: relative;
  color: white;
  font-weight: 500;
  padding-bottom: 0.5rem;
  transition: all 0.3s ease;
}

.nav-link::after {
  content: '';
  position: absolute;
  width: 0;
  height: 2px;
  bottom: 0;
  left: 0;
  background: #facc15;
  transition: width 0.3s ease;
}

.nav-link:hover::after {
  width: 100%;
}

.nav-link:hover {
  color: #facc15;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.animate-fade-in {
  animation: fadeIn 1s ease-out forwards;
}

@media (max-width: 640px) {
  .modal-content {
    width: 95%;
    padding: 1.5rem;
  }

  #nav-menu {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 64px;
    left: 0;
    width: 100%;
    background: #1e3a8a;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
    padding: 1rem 0;
  }

  #nav-menu.active {
    display: flex;
  }

  #nav-menu li {
    margin: 1rem 0;
    text-align: center;
  }

  #nav-menu a {
    font-size: 1.2rem;
    padding: 0.75rem 1rem;
    display: block;
    color: white;
  }

  #calculation-section h2 {
    font-size: 2.5rem;
  }

  .grid-cols-1.md\\:grid-cols-2.lg\\:grid-cols-3 {
    grid-template-columns: 1fr;
  }

  #calculation-section input,
  #calculation-section select {
    padding: 0.75rem;
  }

  #calculation-section button {
    padding: 0.75rem 1.5rem;
  }
}

@media (min-width: 640px) {
  #menu-toggle {
    display: none;
  }

  #nav-menu {
    display: flex !important;
  }
}