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What do you think the hardest thing to make in a video game is? You'd be surprised...

A group of video game developers (the people who make video games) started a discussion on social media to talk about the things they find tricky to make in games.

One of the things they all agreed on was: doors - yep the things we open and close to leave or enter a room!

"Doors are complicated to have in games and have all sorts of possible bugs." said indie game developer Stephan Hövelbrinks.

Whether they worked for a big AAA game studio, or a small Indie games studio, many developers said that making doors in video games was tricky and time-consuming - but why is this?

Non-player characters (or NPCs) in video games move on something called a 'navigation mesh' or 'navmesh' for short - which is used to tell a character where it's allowed to walk around in a space.

Each room or area in a game has a navmesh, but the trouble with a door is that it creates a blocker or a split between two of these meshes.

As a character opens a door and moves from one navigation mesh to another, they are at risk of getting 'lost' if they don't connect to the next navigation mesh.

This can cause all sorts of bugs in the game, like the character might end up running on the spot, or flying up and down because they are not attached to a navigation mesh which tells them where they can walk.

Many games do not add doors for this reason, as they can take a long time to make, and fix the bugs that they can create.

They can also cause other issues such as lining up the character's hands with the door to open it, and how it closes, as well as how the door sounds when it opens and closes.

So, whenever you open a door in a video game, spare a thought for the developers who helped to make it happen!