I sketched this straight onto the back of half a sheet of A4 drawing paper and cut it out with a craft knife, then photographed it mostly by staging it on a pile of books under my desk, turning off the ceiling light, lighting the theatre with a desk lamp under my chin and lying stretched out on the floor to take a photo without a flash. My housemates took this remarkably calmly.
Then I played around with Photoshop.
This is another version with part of the pile of books:
And here is a less tampered-with photo of the theatre.