We’ve talked a lot over the years about the “don’t break the chain” method of habit building, where you visually mark the completion of a habit each day to help you keep it going. The classic method is to put an “X” on a paper calendar every day. The longer your streak lasts, the more motivated you’ll be to keep it up, as anyone who’s had a Snapchat streak with a friend knows.

Paper is great for this, granted, but some people prefer digital tools. That’s why I like Habo, an open-source habit tracking app for Android and iPhone that couldn’t be simpler. There are no ads and no upselling, it’s just a way to help build habits. Once you download and open the app, you add as many habits as you want. The idea is that you check things off as you do them.

At the top of each habit is an indicator that shows how many days your streak has lasted. And you can configure the settings to do things no paper calendar can, like reminding you of your habit at a certain time every day. For example, you want to do 20 push-ups before lunch every day. You can set the app to notify you at 11:55 a.m. You can also add specific details about your routine and the reward you give yourself for completing it.

What I really like about this app is its simplicity, and the fact that it is completely free. Too many productivity tools get unnecessarily complicated when they are after money. Habo does what you need and nothing else.