You can include any activity you want: reading books, programming, learning, playing on piano, even exercises.
Chain is a streak of activities done everyday.
You can either use it to make new habits by making sure you don't break the chain.
Or to break existing habits by breaking the chain.
The choice is yours.
The application enables you to create, change name, make colors, manage chains. Every chain is a single activity. "Don't break the chain" saves progress automatically and displays awesome statistics ;)