At any one time, your Gamer's Brainboard / Arduino can hold one "Sketch" at a time. A sketch is a set of instructions that tells the board what functions it needs to perform.
Here's an example from the Write your Name project found over on Club Make
What this means, is any new code you upload will automatically replace the current "Sketch". For example, if you decide to upload the code of the next project Draw an Emoji or decide to load one of the retro games, what is currently displayed on your Gamer will be replaced with the new sketch.
As you work on different sketches simply save them to your computer and re-upload them anytime you'd like to pick up where you left off.
Still got questions? Drop us a line here and we'll be more than happy to help!