body {
  font-family: 'Segoe UI', 'Helvetica Neue', sans-serif;
  background: #f5f5f5;
  margin: 0;
  padding: 0;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.todo-app {
  background: #fff;
  width: 90%;
  max-width: 500px;
  margin: 20px;
  padding: 24px;
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

h1 {
  color: #333;
  text-align: center;
  margin-bottom: 24px;
  font-size: 1.8rem;
}

#todo-form {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
}

#todo-input {
  flex: 1;
  padding: 12px;
  border: 2px solid #e0e0e0;
  border-radius: 6px;
  font-size: 1rem;
  transition: border-color 0.3s;
}

#todo-input:focus {
  outline: none;
  border-color: #4a90e2;
}

#todo-form button {
  padding: 12px 24px;
  background: #4a90e2;
  color: white;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-size: 1rem;
  transition: background-color 0.3s;
}

#todo-form button:hover {
  background: #357abd;
}

#todo-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px;
  border-bottom: 1px solid #eee;
  transition: all 0.3s ease;
}

.todo-item:hover {
  background-color: #f8f9fa;
}

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

.task-text {
  flex: 1;
  font-size: 1rem;
  color: #333;
  transition: all 0.3s ease;
}

.todo-item.completed {
  background-color: #f5f5f5;
  opacity: 0.7;
}

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

.delete-btn {
  background: none;
  border: none;
  color: #e74c3c;
  cursor: pointer;
  font-size: 1.1rem;
  padding: 4px 8px;
  border-radius: 4px;
  transition: background-color 0.3s;
}

.delete-btn:hover {
  background-color: #ffebee;
}

@media (max-width: 600px) {
  .todo-app {
    width: 95%;
    margin: 10px;
    padding: 16px;
  }

  h1 {
    font-size: 1.5rem;
  }

  #todo-form {
    flex-direction: column;
  }

  #todo-form button {
    width: 100%;
  }
}