Super Mario 64’s Cool, Cool Mountain is probably one of the most iconic snow levels in gaming history, but did you know that people have spent the past 28 years trying to get through a single door? That is until earlier this week, when a Youtuber named pannenkoek2012 uploaded a video explaining how to get through without any cheats or hacks—just the help of one bouncy penguin.

Now I know what you must be thinking: What door could possibly be so important that a community spends the better part of three decades trying to unlock it? Well, it’s the single least important door in the world. In fact, it’s the reverse side of the door Mario exits after getting the star at the end of the slide section of the level. That’s right, we’ve actually all been on the other side of the door and know damn well what it’s hiding—it’s just we haven’t been able to get back in.

Once you exit the door, you’re dropped right back into the main section of the level, next to the mother penguin who insists you find her kid and bring them back to her. The problem is the outside of the door doesn’t have a knob, and doesn’t allow you back through. Though I remember trying to go back through the door and failing as a kid, I didn’t realize that some folks hadn’t just moved on from it. Now, pannenkoek2012 has cracked this decades-long quest wide open thanks to some light platforming and knowledge of Super Mario 64’s coding logic.

According to their video, the biggest impediment to opening the door from the outside is the fact that the cabin walls around the entrance have collision that literally blocks the way to it. If you’ve ever tried to open the door yourself, you’ll know that Mario just kind of winds up shimmying against an invisible wall in front of the door. However, by hacking the game and removing the walls, pannenkoek2012 discovered that simply walking up to the door would open it, which led them to consider if it might be possible to open without hacks.

It turns out that by manipulating the game’s logic, you absolutely can open the door. The door’s hitbox (and this is true of every door in the game) requires that Mario be walking into the door in order to open it. Since the cabin walls’ collision barred Mario from interacting with the hitbox, it’s physically impossible to accomplish by normal means. But by manipulating the AI of the mother penguin (whose hitbox pushes Mario outwards) it’s possible to just barely clip Mario into the door enough to have him open it. Though players have found that jumping over the mother penguin into the door would send Mario free falling through the level’s geometry, someone who goes by the Discord username Alexpalix1 discovered that by turning around immediately after the free fall (which sets Mario’s condition to walking), you would miraculously be able to collide with the door’s hitbox and open it from the outside.

Naturally, pannenkoek2012 tried to apply this newfound exploit to speedrunning and see if it was a quicker strategy than the pre-established route. Though they found that it didn’t really save time, the discovery of the tech itself could pave the way for optimizations down the road.

Even though the door leads to a room we’re all very familiar with, and contains no secrets, it’s always neat to see communities come together to solve mysteries like this. Super Mario 64 players in particular have been trying to crack that game wide open for a long while now, and seeing the fruits of their labor is always pretty incredible. You’d think that after all this time the game would run out of ways to keep surprising us, but its most diehard fans have kept it alive and entertaining for 28 years and counting.