I have had an M40 for 2 days now, but I've learned more in those days of coarse than most of the reading that I've done. You can turn down the screen brightness just by letting the M40 do it automatically in stages, as the battery loses power, or you can just hit the fn+F6 key to turn down the brightness with a function key, or hit the fn+F7 key to make it brighter.
The manual for this computer is a bit flakey, but you get that with these sorts of products, where it looks like it was written by someone with grade 3 English skills, and who also doesn't really know the product.
In the manual, it warns you not to charge the battery longer than fully recharged status, but in another place, the say that once it glows blue it indicated full charge, and it won't continue to charge with the DC-in connected to the AC transformer. In another part of the manual, it talks about it glowing green, when in fact, the indicator light never ever glows green. It glows amber and blue, but not green. Really I'm left not knowing whether or not I'm damaging my battery by leaving it plugged in and off to charge when the battery is fully charged. If it does damage the battery, then it is a significant flaw in my opinion, since then you sort of have to babysit the battery, and I would like to be able to put in on charge and then go to bed for the night, and leave it charge until morning, so that I have a full charge in the morning. Since it can charge in 3 hours, I don't like the idea of having to wake up at 3AM to unplug the computer, as I have done. I was VERY annoyed by this STUPID flaw, if in fact this is what has to be done.
Because if you want to save your battery, and you have it plugged in AC, then you shouldn't expect it to be damaging your battery, or trying to charge it. The battery indicator will glow blue, and the manual says that it won't charge. The manual also says that when it glows blue and the computer is off but plugged in that it should glow blue, and there will be no charge. So it seems somehow that the manual is contradicting itself on this important issue. That's my main complaint with this computer.