Around 3 hours usually, but it can be completed in under a hour if you know what you're doing.
Recent community posts
Hello, thank you for playing, i'm sorry but only the latest version of Gzdoom is supported, even if your friend were to pass the OpenGL check, it still wouldn't run because that version of the engine is extremely outdated and would lack a lot of features used to make this project. Your best bet is to tell them to run it with LZDoom instead (you can find it in the same page of Gzdoom), but keep in mind that that's not supported as well so it will not look and play the same.
Thanks for playing, the last puzzle doesn't reset if you die, so in your case, after exiting the basement, you've already got the first laugh and you can start straight away by getting the second laugh instead.