Add a task, then add a subtask under it. Keep going until each piece is small enough to start without thinking. Parents can be collapsed so the list stays readable, and you can collapse a whole project when you are not working on it.
Any task can be a parent, at any depth.
Collapse a parent to hide its whole branch, expand it to see the detail again.
Drag a task to reorder it, or drop it under a different parent to restructure the plan without retyping anything.
The project shows one percentage averaged across all of its tasks and subtasks, so sliding any subtask moves it.
Everything syncs between the web app and the Android app.