The light green colour for on focus todos seems too subtle. Maybe a thicker border and brighter background colour?
When a todo item is ticked, the pending tasks number is not amended.
Also, the switch to a dark background colour is drawing attention to the completed completed. Maybe new todos are dark coloured, and completed ones are lighter in colour?
The CLEAR ALL button automatically clears all todos, so there is not really a need to add a warning that all todos will be cleared. Maybe add a confirmation prompt before clearing all tasks?
How about adding completed tasks to a trash list, this way completed and incomplete todos are listed separately?