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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #f5f5f5;
  color: #333;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding-top: 80px;
}

.container {
  width: 100%;
  max-width: 520px;
  padding: 0 16px;
}

h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 24px;
}

#add-form {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
}

#add-form input {
  flex: 1;
  padding: 10px 14px;
  font-size: 1rem;
  border: 1px solid #ddd;
  border-radius: 8px;
  outline: none;
  transition: border-color 0.15s;
}

#add-form input:focus {
  border-color: #666;
}

#add-form button {
  padding: 10px 20px;
  font-size: 1rem;
  background: #333;
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.15s;
}

#add-form button:hover {
  background: #555;
}

#todo-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  background: #fff;
  border-radius: 8px;
  border: 1px solid #eee;
}

.todo-item input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
  accent-color: #333;
}

.todo-item .title {
  flex: 1;
  font-size: 1rem;
  cursor: text;
}

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

.todo-item .delete-btn {
  background: none;
  border: none;
  color: #ccc;
  font-size: 1.2rem;
  cursor: pointer;
  padding: 0 4px;
  transition: color 0.15s;
}

.todo-item .delete-btn:hover {
  color: #e55;
}

.empty-state {
  text-align: center;
  color: #999;
  padding: 40px 0;
  font-size: 0.95rem;
}