Maybe it was easier for me because I've played it on easy skill, but instead of running forward to climb the ramps, I've turned my back to the ramps, ran backwards over the ramps, and then pressed +forward immediately after jumping. This was way easier than trying to do a 180� turn in mid air. 

I'll try again. 

I've found at least one shootable button in a pitch black spot.

Every button in dark area has a minlight on it or a light source near it.

By the way, it was impossible for me to jump to the highest part of the crusher to reach the last rune, so I just noclipped it. Trying to jump from the wall light didn't help.

It is possible. Other secrets are hard to find, easy to reach type, this one is the opposite type. It's easy to find but you have to find a way to reach it. Use environments around. That crusher has lowered damage and a respawning health near it to allow multiple tries.

Also I think that my default setup is brighter than most of others. Will have this in mind when lighting future maps. I was just blown away when discovered bounce lighting. Made previous two maps with just bounced lighting and no fill lights for contrast dramatic lighting. Though a lot of people found it to be too dark. 

Hah thanks man, creating those func_trains made me insane so maybe that's why I decided to punish everyone. <_> 

Every button in dark area has a minlight on it or a light source near it.

See this (sorry for the hi-res/low-res texture mishmash):
Screenshot 1
Screenshot 2 

Oh yeah, it was that button that made me realize that I'll have to devote a lot of time for the rest.

It sorta kinda has a clue, but I'm not sure it was even intentional. 

One good reason to use DP+SMC: Seven's mod includes a flashlight... 

BTW mankrip, I actually CAN see a faint red glow from the star on the button in your first pic... 

I found that button (by accident, more or less), and even I wasn't able to see it before I saw the second shot. 

I can see that button on my setup, it has minlight 50 (or 70, will check when I get home). and that screenshot looks way more dark than what I see on my system (gamma 0). 

I actually had to open that screenshot in GIMP and do a "selection by color" to find out what you were talking about. That's the darkest red color in the whole Quake palette (0A0000, index 64).
Screenshot 

I'm looking at this screenshot on my work pc. I need to compare it to what I will see on it when I get home 

though I really have to pay extra attention to see it. Maybe you need to adjust your monitor's brightness/contrast? Or you need glasses... ;p 

I've made an experiment: I made a screenshot (where I can clearly see the button), watched it on my monitor and watched it on my tablet. I couldn't find the button when watcing the screenshot from my tablet, tho I can see the button and the box from my monitor. The other thing is that I can't see the button on your screenshot even on my monitor therefore your engine provides a darker picture than QS or Mark V.

On the other hand I need to calibrate my monitor. 

Mark V screenshots:
Screenshot 1
Screenshot 2

It has nothing to do with my renderer; the lighting in my renderer is still faithful to the vanilla software renderer. 

To be fair, I can see it slightly better on your Mark V screenie. I have a hunch that it may be due to your dithering: in your Super8 screenshot, red dots are mixed with black dots. 

The button beneath the retracting floor bars was a little tough to spot and there wasn't enough room on the crusher ride up, but the exploration was fun. There is plenty of nice, clean architecture to jump around on.

Loved that building sinking into the lava!

Now, on to the others...