Falling images get "stuck" when using a wide browser window

[salamanders]

I've got a simple "falling random images" setup. http://jsfiddle.net/salamanders/sdnfwm25/ works great.
Until I try to do it full-screen. Then the images on the right-ish side get stuck, and the images in the left-ish side fall like normal. Maybe a hidden effect of some canvas size constant?

The problem only happens when the canvas is big enough.

(Best way I've found to try full-screen is the mobile debugger to the right of the "run" button in jsfiddle.)

[liabru]

See issue #67, thanks.