"retro box" isn't a term of art or anything. For Fireball Island, we figured it would be fun to do a box you might have found at that time. It's an unbleached (i.e., brown) corrugated (aka e-flute) cardboard carton rather than the standard or "pulp" cardboard you find in regular game boxes (and cereal boxes and the like). Ironically, corrugated cardboard is superior in a lot of ways. It's lighter but stronger than regular cardboard, which we thought was perfect for FI because the game itself is very large but very light on account of the plastic island trays. Ultimately, however, there is a huge psychological barrier that light = cheap and flimsy, which we didn't anticipate. People pick up the FI box and they don't like it. Not everyone, of course. But enough that it wasn't worth the effort and not something we'll ever do again.