Super Mario 64 has a number of impossible coins - that is, coins that are impossible to collect. Well, it looks like the mystery around one of them has been solved 20 years after the groundbreaking platformer came out.
YouTube channel UncommentatedPannen documents an impossible coin found in the huge version of Tiny-Huge Island. In one section of the level, there is a line of four coins. So what? Well, everywhere else in the game, coins line up horizontally in fives.
So what happened to the fifth coin in this particular line? UncommentatedPannen explains that the fifth coin immediately despawns after Mario comes close enough to spawn it because the spawn marker is positioned too far below the slope.
The video, below, goes into the detail. Basically, SM64 works out where to place coins by determining the distance between where the coins spawn and the position of the ground. But in this case, the spawn marker is so far below the ground that the coin placed at the most uphill point in the horizontal line spawns below the ground, thus triggering a failsafe that forces it to disappear.
UncommentatedPannen speculates that this anomaly is the result of the geometry being changed during development. At first, there was no slope. But after the slope was added, the developers at Nintendo simply forgot to adjust the spawn marker.
Either way, it's a cool revelation for a video game that just keeps on giving. Not only are players finding new ways to speerdun Nintendo's platformer, but they're still working out how the whole thing works.