Struggling to fall asleep? Noticed your kids getting hyperactive after using tablets before bedtime? If you're using your smartphone or tablet in the evening, or if you're sensitive to light during migraines, Twilight might be the solution you need!

Recent research indicates that exposure to blue light before sleep can disrupt your natural circadian rhythm, making it harder to fall asleep. This is due to a photoreceptor in your eyes known as Melanopsin, which is sensitive to blue light in the 460-480nm range. This light can suppress the production of Melatonin, a crucial hormone for maintaining healthy sleep-wake cycles. Studies have shown that reading on a tablet or smartphone for a couple of hours before bed can delay sleep by about an hour.

The Twilight app adjusts your device's screen to the time of day, filtering out blue light after sunset and applying a soothing red filter to protect your eyes. This filter's intensity smoothly transitions according to your local sunrise and sunset times. Twilight is also compatible with Wear OS devices.

For more detailed information, visit the documentation at http://twilight.urbandroid.org/doc/.

Enhance Your Experience with Twilight

1) Bed Reading: Twilight offers a more comfortable night reading experience by dimming the screen beyond what standard backlight controls allow.

2) AMOLED Screens: Twilight has been tested on AMOLED screens for five years with no signs of screen depletion or over-burning. When configured correctly, it emits less light and distributes it more evenly across the screen, potentially increasing the lifespan of your AMOLED display.

To understand more about circadian rhythms and the role of melatonin, you can visit these Wikipedia pages:

• Melatonin
• Melanopsin
• Circadian Rhythms
• Circadian Rhythm Disorder

Permissions Required by Twilight

• Location: To determine your local sunset and sunrise times.
• Running Apps: To pause Twilight in selected applications.
• Write Settings: To adjust the screen's backlight.
• Network: To connect with smart lighting systems like Philips HUE to adjust household lighting.

Accessibility Service

For comprehensive screen filtering, including notifications and the lock screen, Twilight may request to enable its Accessibility Service. Rest assured, this service is used solely to enhance screen filtering and does not collect any personal data. Learn more at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/.

Wear OS Integration

Twilight syncs with your Wear OS device, allowing you to manage the filter settings directly from a "Wear OS Tile".

Automation with Tasker

For further customization, explore automation options with Tasker at https://sites.google.com/site/twilight4android/automation.

Relevant Scientific Research

• Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans - Derk-Jan Dijk, et al. (2012)
• Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans - Joshua J. Gooley, et al. (2011)
• Effect of Light on Human Circadian Physiology - Jeanne F. Duffy, Charles A. Czeisler (2009)
• Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans - Claude Gronfier, et al. (2009)
• Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans - Kenneth P. Wright, et al. (2009)
• The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work - Nayantara Santhi, et al. (2008)
• Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina - Farhan H. Zaidi, et al. (2007)