This is generally bad javascript code written by someone who barely knows javascript.
You probably shouldn't use it to learn from, let alone use it in your own projects.
However, you may use it in non-commercial projects.

- If you choose to use any of the code in a non-commercial project,
  please give credit to YukieVT.
- Don't use the code for anything commercial.
- Don't use the code for any political campaign.
- Don't use the assets (sounds, images) for any project, even non-commercial ones.