It is very important in a game that you detect collisions properly. Nobody is going to play a game where things start exploding even when they are many pixels apart. Besides the graphics and sounds, this is one more thing that you should try to keep as accurate as possible.
Just like images or sprites, sound also plays a vital role in games. The right background music can set the mood for the game. Similarly, including sound effects for things like a crash or gunfire will make the game much more interesting.
In all the Crafty tutorials up to this point, you have been using square or rectangular boxes to understand different concepts like animation and keyboard or touch events. While this is a great way to quickly learn more about the library, you will most probably like to use images in your actual games.
In the last Crafty series, you learned about different ways of moving elements around using the keyboard. While a keyboard can help you create a variety of games, some situations require you to control different mouse events to make the game more enjoyable.