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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: #333;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 0;
}

.logo {
  font-size: 1.8rem;
  font-weight: bold;
  color: #667eea;
  text-decoration: none;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 2rem;
}

.nav-links a {
  text-decoration: none;
  color: #333;
  font-weight: 500;
  transition: color 0.3s ease;
}

.nav-links a:hover {
  color: #667eea;
}

.auth-buttons {
  display: flex;
  gap: 1rem;
}

.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: 25px;
  cursor: pointer;
  font-weight: 600;
  text-decoration: none;
  display: inline-block;
  text-align: center;
  transition: all 0.3s ease;
}

.btn-primary {
  background: linear-gradient(45deg, #667eea, #764ba2);
  color: white;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 20px rgba(102, 126, 234, 0.4);
}

.btn-outline {
  border: 2px solid #667eea;
  color: #667eea;
  background: transparent;
}

.btn-outline:hover {
  background: #667eea;
  color: white;
}

.hero {
  text-align: center;
  padding: 4rem 0;
  color: white;
}

.hero h1 {
  font-size: 3.5rem;
  margin-bottom: 1rem;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.hero p {
  font-size: 1.2rem;
  margin-bottom: 2rem;
  opacity: 0.9;
}

.search-container {
  background: white;
  border-radius: 50px;
  padding: 1rem;
  margin: 2rem auto;
  max-width: 600px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
  display: flex;
  gap: 1rem;
}

.search-input {
  flex: 1;
  border: none;
  padding: 0.75rem 1rem;
  font-size: 1rem;
  outline: none;
  border-radius: 25px;
}

.search-btn {
  background: linear-gradient(45deg, #667eea, #764ba2);
  color: white;
  border: none;
  padding: 0.75rem 2rem;
  border-radius: 25px;
  cursor: pointer;
  font-weight: 600;
}

.action-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin: 3rem 0;
}

.action-card {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-radius: 20px;
  padding: 2rem;
  text-align: center;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease;
  cursor: pointer;
}

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

.action-card i {
  font-size: 3rem;
  color: #667eea;
  margin-bottom: 1rem;
}

.action-card h3 {
  color: #333;
  margin-bottom: 1rem;
}

.main-content {
  background: white;
  margin: 2rem 0;
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  overflow: hidden;
}

.tabs {
  display: flex;
  background: #f8f9fa;
  border-bottom: 1px solid #dee2e6;
}

.tab {
  flex: 1;
  padding: 1rem;
  text-align: center;
  cursor: pointer;
  border: none;
  background: none;
  font-weight: 600;
  transition: all 0.3s ease;
}

.tab.active {
  background: white;
  color: #667eea;
  border-bottom: 3px solid #667eea;
}

.tab-content {
  padding: 2rem;
  display: none;
}

.tab-content.active {
  display: block;
}

.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.product-card {
  border: 1px solid #e0e0e0;
  border-radius: 15px;
  overflow: hidden;
  transition: all 0.3s ease;
  background: white;
}

.product-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
}

.product-image {
  width: 100%;
  height: 200px;
  background: linear-gradient(45deg, #f0f0f0, #e0e0e0);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  color: #999;
}

.product-info {
  padding: 1.5rem;
}

.product-title {
  font-weight: bold;
  margin-bottom: 0.5rem;
  color: #333;
}

.product-price {
  color: #667eea;
  font-size: 1.2rem;
  font-weight: bold;
  margin-bottom: 0.5rem;
}

.product-condition {
  color: #28a745;
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.product-actions {
  display: flex;
  gap: 0.5rem;
}

.btn-small {
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
  border-radius: 20px;
}

.filters {
  background: #f8f9fa;
  padding: 1.5rem;
  border-radius: 10px;
  margin-bottom: 2rem;
}

.filter-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  align-items: end;
}

.filter-group {
  display: flex;
  flex-direction: column;
}

.filter-group label {
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: #333;
}

.filter-group select,
.filter-group input {
  padding: 0.75rem;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  font-size: 1rem;
  transition: border-color 0.3s ease;
}

.filter-group select:focus,
.filter-group input:focus {
  outline: none;
  border-color: #667eea;
}

.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.7);
  z-index: 2000;
  justify-content: center;
  align-items: center;
}

.modal-content {
  background: white;
  border-radius: 20px;
  padding: 2rem;
  max-width: 500px;
  width: 90%;
  max-height: 80vh;
  overflow-y: auto;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid #e0e0e0;
}

.close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: #999;
}

.form-group {
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: #333;
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 0.75rem;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  font-size: 1rem;
  transition: border-color 0.3s ease;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: #667eea;
}

.online-users {
  position: fixed;
  top: 120px;
  right: 20px;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  padding: 1rem;
  border-radius: 15px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  min-width: 200px;
}

.user-indicator {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: #28a745;
  font-weight: 600;
}

.status-dot {
  width: 10px;
  height: 10px;
  background: #28a745;
  border-radius: 50%;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0% {
    opacity: 1;
  }
  50% {
    opacity: 0.5;
  }
  100% {
    opacity: 1;
  }
}

.swap-indicator {
  background: linear-gradient(45deg, #ff6b6b, #feca57);
  color: white;
  padding: 0.3rem 0.8rem;
  border-radius: 15px;
  font-size: 0.8rem;
  font-weight: bold;
}

.footer {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  margin-top: 3rem;
  padding: 2rem 0;
  text-align: center;
  color: #666;
}

@media (max-width: 768px) {
  .nav-links {
    display: none;
  }

  .hero h1 {
    font-size: 2.5rem;
  }

  .search-container {
    flex-direction: column;
  }

  .filter-row {
    grid-template-columns: 1fr;
  }

  .online-users {
    position: static;
    margin: 1rem 0;
  }
}