$ todo help
Usage:
add <task>
list
completed <id>
delete <id>
$ todo add task1
add: task1
$ todo add task2
add: task2
$ todo list
[ ] 1: task1
[ ] 2: task2
$ todo completed 1
completed: task1
$ todo list
[✓] 1: task1
[ ] 2: task2
$ todo delete 1
deleted: task1
todo list
[ ] 1: task2