Due to some ongoing website issues, we will be performing maintenance on the PhET website over the next few nights (Mountain Daylight time). This will affect only parts of the site, specifically logging in, some activity pages, etc. It should not affect the simulations. We expect that the maintenance will last over an hour. During this time, some parts of PhET may experience periods of unavailability. If you experience persistent issues, please e-mail the PhET Help Desk at firstname.lastname@example.org.
Thanks for your patience.