you said existing media can be used, does that include media that's not made by you? (Ex. Using music from a Mario game)
Yes, it applies to code, images, and sound, but if you follow a very basic tutorial for code or something and change it a lot then that will be allowed. We don’t want 35 identical platformers with that stupid eye character. For images and sound if they are under a CC License or are royalty free then its fine