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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 40px 20px;
}

.container {
  background: white;
  border-radius: 16px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
  width: 100%;
  max-width: 500px;
  padding: 30px;
}

header {
  text-align: center;
  margin-bottom: 30px;
}

header h1 {
  color: #333;
  font-size: 2rem;
  margin-bottom: 5px;
}

header p {
  color: #666;
  font-size: 0.9rem;
}

.input-section {
  margin-bottom: 25px;
}

#todo-form {
  display: flex;
  gap: 10px;
}

#task-input {
  flex: 1;
  padding: 12px 16px;
  border: 2px solid #e0e0e0;
  border-radius: 8px;
  font-size: 1rem;
  transition: border-color 0.3s;
}

#task-input:focus {
  outline: none;
  border-color: #667eea;
}

.btn-add {
  padding: 12px 24px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
}

.btn-add:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.btn-add:active {
  transform: translateY(0);
}

.tasks-section h2 {
  color: #333;
  font-size: 1.2rem;
  margin-bottom: 15px;
  padding-bottom: 10px;
  border-bottom: 2px solid #f0f0f0;
}

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

.todo-item {
  display: flex;
  align-items: center;
  padding: 15px;
  background: #f9f9f9;
  border-radius: 8px;
  margin-bottom: 10px;
  transition: background 0.2s;
}

.todo-item:hover {
  background: #f0f0f0;
}

.todo-item.completed {
  opacity: 0.7;
}

.todo-item.completed .task-text {
  text-decoration: line-through;
  color: #999;
}

.task-checkbox {
  width: 20px;
  height: 20px;
  margin-right: 15px;
  cursor: pointer;
  accent-color: #667eea;
}

.task-text {
  flex: 1;
  color: #333;
  font-size: 1rem;
}

.task-actions {
  display: flex;
  gap: 8px;
}

.btn-complete, .btn-delete {
  padding: 6px 12px;
  border: none;
  border-radius: 6px;
  font-size: 0.85rem;
  cursor: pointer;
  transition: transform 0.2s, opacity 0.2s;
}

.btn-complete {
  background: #4caf50;
  color: white;
}

.btn-complete:hover {
  transform: scale(1.05);
}

.btn-delete {
  background: #f44336;
  color: white;
}

.btn-delete:hover {
  transform: scale(1.05);
}

.empty-message {
  text-align: center;
  color: #999;
  padding: 30px;
  font-size: 1rem;
}

.hidden {
  display: none;
}

.actions {
  margin-top: 25px;
  text-align: center;
}

.btn-secondary {
  padding: 10px 20px;
  background: #f0f0f0;
  color: #333;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-secondary:hover {
  background: #e0e0e0;
}