Here's the schematic, sans useless button. Could it be any simpler? . . .

Results

The first night I tried it, I had the lights set too bright, and it woke me out of deep sleep. I was groggy and I had to take it off.

Next night, I had the lights dimmer, but not dim enough. The mask woke me up only out of dreams - excellent! This was a very promising result. The timer was set to wait one hour before flashing, and to flash every 15 minutes thereafter.