Several surprises came to me with this:
(a) How hard it is to figure a simple one like 13 + 6 = ? when half-way asleep!
(b) Improvements in my mental math speed! My brain has started arriving at the answers without consciously calculating. Thankfully the app allows increasing the math difficulty levels. I am now at the level of 67 + 54 = ? LOL!
(c) After having used this for several months with a consistent wake up time, it is not painful to wake anymore, even without the alarm. I never knew I could get there.
[1] https://play.google.com/store/apps/details?id=com.alarmclock...
[2] I am in no way associated with the above app. Plus, I am sure there would be many with the same feature.
But if I allow myself to get up after 6 hours of sleep a combination of having drank too much before going to bed and not closing the blinds works best. I know that sleeping in perfect darkness is supposed to be a good thing. But getting up in the darkness doesn't work so well for me. The need to pee is a strong motivator as well.