Hows it done? Photo challenge.

[Anbesol]

I was photographing some products today. Decided to try something a little goofy and see what kind of effects I could create. I came up with something I kind of like, but the effect is very bizarre. At first I didn't even realize exactly how I did it, and I looked around a bit a little dumbfounded, but I eventually realized exactly what happened.

So here is the challenge, explain exactly how the effect happened.

The scene was simply a keyboard and mouse placed on a white posterboard. They were both entirely in the frame. I used two remote wireless flashguns.

[SmartWombat]

Hm, looks like you didn't use manual control to override the camera's shutter speed.
Guessing from the yellow/brown blur that you have tungsten light in the room.
So that the camera decided to expose for the background, and then you blitzed the background with two flashes.
The brownish blur is camera movement.

[Anbesol]

Actually I did shoot this full manual, the yellow brown is from a tungsten light, but there was 2 flashguns that helped me achieve the effect.

I'll go ahead and give the metering data as a clue - f/4.5, 1.6 second, ISO 200. I dragged the shutter and it was handheld. The part that confused me at first was the sharp solid lines that intersected the keyboard. Which is the puzzler here. Keep in mind, the entire keyboard was in the frame. I did not cover the keyboard as it appears in this image, it simply sat right on top of a white posterboard.