* {
  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: 1200px;
  margin: 0 auto;
  padding: 20px;
}

.header {
  text-align: center;
  color: white;
  margin-bottom: 40px;
}

.header h1 {
  font-size: 2.5rem;
  margin-bottom: 10px;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

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

.exercises-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 30px;
  margin-bottom: 40px;
}

.exercise-card {
  background: white;
  border-radius: 15px;
  padding: 30px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.exercise-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
}

.exercise-title {
  font-size: 1.5rem;
  color: #667eea;
  margin-bottom: 15px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.exercise-number {
  background: #667eea;
  color: white;
  width: 35px;
  height: 35px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
}

.exercise-description {
  color: #666;
  margin-bottom: 20px;
  line-height: 1.7;
}

.exercise-features {
  list-style: none;
  margin-bottom: 25px;
}

.exercise-features li {
  padding: 8px 0;
  padding-left: 25px;
  position: relative;
  color: #555;
}

.exercise-features li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: #4caf50;
  font-weight: bold;
}

.exercise-link {
  display: inline-block;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  text-decoration: none;
  padding: 12px 25px;
  border-radius: 25px;
  font-weight: 600;
  transition: all 0.3s ease;
  text-align: center;
}

.exercise-link:hover {
  transform: scale(1.05);
  box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.main-content {
  background: white;
  border-radius: 15px;
  padding: 40px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  margin-bottom: 30px;
}

.section-title {
  font-size: 2rem;
  color: #333;
  margin-bottom: 20px;
  text-align: center;
}

/* User Profile Section */
.user-profile-section {
  margin-bottom: 40px;
  padding: 25px;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  background: #f9f9f9;
}

.user-search-form {
  display: flex;
  gap: 15px;
  margin-bottom: 20px;
  align-items: center;
  flex-wrap: wrap;
}

.user-id-input {
  padding: 12px 15px;
  border: 2px solid #ddd;
  border-radius: 8px;
  font-size: 16px;
  min-width: 200px;
  transition: border-color 0.3s ease;
}

.user-id-input:focus {
  outline: none;
  border-color: #667eea;
}

.search-user-btn {
  background: #667eea;
  color: white;
  border: none;
  padding: 12px 20px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 16px;
  font-weight: 600;
  transition: background 0.3s ease;
}

.search-user-btn:hover {
  background: #5a6fd8;
}

.user-profile-card {
  background: white;
  border-radius: 10px;
  padding: 25px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
  display: none;
}

.user-profile-card.show {
  display: block;
}

.user-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: #667eea;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 2rem;
  font-weight: bold;
  margin: 0 auto 20px;
}

.user-info {
  text-align: center;
}

.user-name {
  font-size: 1.5rem;
  color: #333;
  margin-bottom: 10px;
}

.user-details {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 15px;
  margin-top: 20px;
}

.user-detail-item {
  background: #f5f5f5;
  padding: 10px 15px;
  border-radius: 8px;
}

.user-detail-label {
  font-weight: 600;
  color: #667eea;
  display: block;
  margin-bottom: 5px;
}

/* Posts Section */
.posts-section {
  margin-bottom: 40px;
  padding: 25px;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  background: #f9f9f9;
}

.posts-container {
  display: grid;
  gap: 20px;
}

.post-item {
  background: white;
  border-radius: 10px;
  padding: 20px;
  box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
}

.post-title {
  font-size: 1.2rem;
  color: #333;
  margin-bottom: 10px;
  font-weight: 600;
}

.post-body {
  color: #666;
  line-height: 1.6;
  margin-bottom: 15px;
}

.post-author {
  font-size: 0.9rem;
  color: #888;
  margin-bottom: 15px;
}

.show-comments-btn {
  background: #4caf50;
  color: white;
  border: none;
  padding: 8px 15px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 14px;
  transition: background 0.3s ease;
}

.show-comments-btn:hover {
  background: #45a049;
}

.comments-container {
  margin-top: 15px;
  padding-top: 15px;
  border-top: 1px solid #eee;
  display: none;
}

.comments-container.show {
  display: block;
}

.comment-item {
  background: #f8f9fa;
  padding: 15px;
  border-radius: 8px;
  margin-bottom: 10px;
  border-left: 4px solid #667eea;
}

.comment-author {
  font-weight: 600;
  color: #667eea;
  margin-bottom: 5px;
}

.comment-email {
  font-size: 0.9rem;
  color: #888;
  margin-bottom: 8px;
}

.comment-body {
  color: #555;
  line-height: 1.5;
}

.load-more-btn {
  background: #ff9800;
  color: white;
  border: none;
  padding: 12px 25px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 16px;
  font-weight: 600;
  margin-top: 20px;
  transition: background 0.3s ease;
  display: none;
}

.load-more-btn:hover {
  background: #f57c00;
}

.load-more-btn.show {
  display: block;
}

/* Todo Section */
.todo-section {
  margin-bottom: 40px;
  padding: 25px;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  background: #f9f9f9;
}

.todo-filters {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.filter-btn {
  background: #e0e0e0;
  color: #333;
  border: none;
  padding: 10px 20px;
  border-radius: 25px;
  cursor: pointer;
  font-size: 14px;
  font-weight: 600;
  transition: all 0.3s ease;
}

.filter-btn.active {
  background: #667eea;
  color: white;
}

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

.todo-stats {
  display: flex;
  gap: 20px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.stat-item {
  background: white;
  padding: 15px 20px;
  border-radius: 10px;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.stat-number {
  font-size: 1.5rem;
  font-weight: bold;
  color: #667eea;
}

.stat-label {
  font-size: 0.9rem;
  color: #666;
  margin-top: 5px;
}

.todo-list {
  display: grid;
  gap: 10px;
}

.todo-item {
  background: white;
  padding: 15px 20px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  gap: 15px;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.todo-item.completed {
  background: #f0f8f0;
  border-left: 4px solid #4caf50;
}

.todo-item.incomplete {
  background: #fff8f0;
  border-left: 4px solid #ff9800;
}

.todo-checkbox {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid #ddd;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  color: white;
  font-weight: bold;
}

.todo-item.completed .todo-checkbox {
  background: #4caf50;
  border-color: #4caf50;
}

.todo-item.incomplete .todo-checkbox {
  background: #ff9800;
  border-color: #ff9800;
}

.todo-text {
  flex: 1;
  color: #333;
}

.todo-item.completed .todo-text {
  text-decoration: line-through;
  color: #888;
}

/* Loading and Error States */
.loading-spinner {
  display: none;
  text-align: center;
  padding: 20px;
  color: #667eea;
  font-weight: 600;
}

.loading-spinner.show {
  display: block;
}

.error-message {
  background: #ffebee;
  color: #c62828;
  padding: 15px;
  border-radius: 8px;
  border-left: 4px solid #c62828;
  margin: 15px 0;
  display: none;
}

.error-message.show {
  display: block;
}

.success-message {
  background: #e8f5e8;
  color: #2e7d32;
  padding: 15px;
  border-radius: 8px;
  border-left: 4px solid #4caf50;
  margin: 15px 0;
  display: none;
}

.success-message.show {
  display: block;
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    padding: 15px;
  }

  .header h1 {
    font-size: 2rem;
  }

  .exercises-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .exercise-card {
    padding: 20px;
  }

  .user-search-form {
    flex-direction: column;
    align-items: stretch;
  }

  .user-id-input {
    min-width: auto;
  }

  .todo-filters {
    justify-content: center;
  }

  .todo-stats {
    justify-content: center;
  }

  .user-details {
    grid-template-columns: 1fr;
  }
}