Definitely as possible today with a canvas covering the entire page but being transparent, probably exactly what they did with the <object> container for that t

Definitely as possible today with a canvas covering the entire page but being transparent, probably exactly what they did with the <object> container for that trick too. Flash was constrained to the container, just like <canvas> is, and surely it wasn't actually "escaping" from that container, but the container was drawn over the entire window. But, hard to know exactly how it was implemented without seeing the source, so I guess we'll never know.