You were on a plane going who knows where and it suddenly started to shake. The plane crashes in the ocean and you were the only survivor. Or the only person there. You swim to a light house and go in hoping there was help. Going inside there was a giant gold statue of someone. 

The plaque at its feet said Andrew Ryan. Going down some stairs you see a chair and a lever going up or down.

Up scenario:

You push the lever up and sit in the chair. The chair formed a rocket of sorts and you were launched

[There should be a GIF or video here. Update the app now to see it.]

(Something like this.)

When the rocket finishes flying you were amazed. A city in the sky?! Now you go through the church thing. The rest is up to you

(Welcome to Columbia.)

Down scenario:

Pulling the lever down and sitting in the chair you go down and the hatch above you close shutting tight. The ball thing goes down and you watch. Through the window a video played and the Andrew Ryan guy talked

[There should be a GIF or video here. Update the app now to see it.]

When the ball thing stopped you see a guy get killed by someone with hooks and talking nonsense. A voice from a nearby radio asked "would you kindly pick up that radio?"

(Welcome to rapture)