:root {
  --primary-color: #1a252f;
  --secondary-color: #27ae60;
  --accent-color: #3498db;
  --bg-color: #f4f7f6;
  --text-color: #333;
  --sidebar-width: 260px;
  --transition: all 0.3s ease;
}

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

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  overflow: hidden;
}

.app-container {
  display: flex;
  height: 100vh;
  width: 100vw;
}

.sidebar {
  width: var(--sidebar-width);
  background-color: var(--primary-color);
  color: white;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
}

.sidebar-header {
  padding: 30px 20px;
  text-align: center;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.sidebar-header h1 {
  font-size: 1.5rem;
  letter-spacing: 2px;
  color: var(--secondary-color);
}

.nav-menu {
  list-style: none;
  padding: 20px 0;
  flex-grow: 1;
}

.nav-item {
  width: 100%;
}

.nav-link {
  display: flex;
  align-items: center;
  padding: 15px 25px;
  color: #bdc3c7;
  text-decoration: none;
  cursor: pointer;
  transition: var(--transition);
}

.nav-link .icon {
  margin-right: 15px;
  font-size: 1.2rem;
}

.nav-link:hover {
  background-color: rgba(255,255,255,0.05);
  color: white;
}

.nav-link.active {
  background-color: var(--secondary-color);
  color: white;
  border-left: 5px solid white;
}

.sidebar-footer {
  padding: 20px;
  border-top: 1px solid rgba(255,255,255,0.1);
}

.main-content {
  flex-grow: 1;
  overflow-y: auto;
  padding: 30px;
  scroll-behavior: smooth;
}

.content-header {
  margin-bottom: 30px;
  border-bottom: 2px solid #ddd;
  padding-bottom: 10px;
}

.content-header h2 {
  font-size: 1.8rem;
  color: var(--primary-color);
}

.tab-content {
  display: none;
  animation: fadeIn 0.4s ease;
}

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

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.card {
  background: white;
  border-radius: 8px;
  padding: 25px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
  margin-bottom: 20px;
}

.btn-export-all {
  width: 100%;
  padding: 12px;
  background-color: var(--accent-color);
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  font-weight: bold;
  transition: var(--transition);
}

.btn-export-all:hover {
  background-color: #2980b9;
}