This course consists of 9 video lectures. Video lengths vary depending on the content allocated to that video. Almost all lectures has challenges inside which students need to solve. All challenges are indicated by the lecturer saying this is a challenge. When you hear that you need to stop the video and to try to solve the challenge. These challenges are based on the information that was taught before in the lecture. All challenges have answers and you can see them by resuming the video after attempting the challenge. Apart from the challenges in the lectures, I strongly advise you to challenge yourself by stopping the video and by trying to implement a feature on your own. Even if you fail to do so, this will improve your Android development and programming skills much further.