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

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  padding: 20px;
}

.container {
  max-width: 500px;
  margin: 0 auto;
  background: white;
  border-radius: 15px;
  padding: 30px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
}

h1 {
  text-align: center;
  color: #333;
  margin-bottom: 30px;
  font-size: 2.5rem;
}

.input-section {
  display: flex;
  gap: 10px;
  margin-bottom: 30px;
}

#todoInput {
  flex: 1;
  padding: 15px;
  border: 2px solid #ddd;
  border-radius: 8px;
  font-size: 16px;
  outline: none;
  transition: border-color 0.3s;
}

#todoInput:focus {
  border-color: #667eea;
}

#addBtn {
  padding: 15px 25px;
  background: #667eea;
  color: white;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  font-size: 16px;
  font-weight: bold;
  transition: background 0.3s;
}

#addBtn:hover {
  background: #5a67d8;
}

.stats {
  display: flex;
  justify-content: space-between;
  margin-bottom: 20px;
  padding: 15px;
  background: #f8f9fa;
  border-radius: 8px;
}

.stat {
  text-align: center;
}

.stat-number {
  font-size: 24px;
  font-weight: bold;
  color: #667eea;
}

.stat-label {
  font-size: 12px;
  color: #666;
  text-transform: uppercase;
}

.todo-list {
  list-style: none;
}

.todo-item {
  display: flex;
  align-items: center;
  padding: 15px;
  margin-bottom: 10px;
  background: #f8f9fa;
  border-radius: 8px;
  border-left: 4px solid #667eea;
  transition: all 0.3s;
}

.todo-item.completed {
  opacity: 0.6;
  border-left-color: #28a745;
}

.todo-item.completed .todo-text {
  text-decoration: line-through;
  color: #666;
}

.todo-checkbox {
  margin-right: 15px;
  width: 20px;
  height: 20px;
  cursor: pointer;
}

.todo-text {
  flex: 1;
  font-size: 16px;
  color: #333;
}

.delete-btn {
  background: #dc3545;
  color: white;
  border: none;
  padding: 8px 15px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 14px;
  transition: background 0.3s;
}

.delete-btn:hover {
  background: #c82333;
}

.empty-state {
  text-align: center;
  padding: 40px;
  color: #666;
  font-style: italic;
}

.filters {
  display: flex;
  justify-content: center;
  gap: 10px;
  margin-bottom: 20px;
}

.filter-btn {
  padding: 8px 16px;
  border: 2px solid #667eea;
  background: white;
  color: #667eea;
  border-radius: 20px;
  cursor: pointer;
  font-size: 14px;
  transition: all 0.3s;
}

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