Warning: a very small percentage of people may experience a seizure when exposed to flashing lights or visual patterns. Even people who have no history of seizures or epilepsy may have an undiagnosed condition that can cause photosensitive epileptic seizures while using such a device. If you or any of your relatives have a history of seizures or epilepsy, it is recommended that you consult a doctor first.
Mind machines (also called "brain machines") are devices with goggles that flash lights and earphones that play sounds meant to entrain the brain into desired frequencies (e.g. alpha for meditation, or delta for deep sleep).
Mind machines were already available for home use in the 90s, but for more than a decade now (e.g. Mitch Altman / Lady Ada*), hobbyists have the ability to build them. Let's build one too (and let's try and figure out what we're doing).