Changes made for this site (original: https://github.com/susam/invaders @ a8830218e7a9034ac7d671f436abd4d6e30e8066)
- Copied invaders.html as index.html, plus LICENSE.md unchanged.
- On the in-game info screen, clicking the source-code link now opens it in a new tab
  (window.open(..., '_blank', 'noopener')) instead of navigating the game frame away.
No other changes. Game logic, graphics, audio and the author's credit/licence screen are unchanged.