You're an archaeologist working at the ruins of what appears to be an ancient, possibly advanced, civilization, and you've just been tasked to investigate a cave.
Well, it's not really a cave, per se - it's just one tunnel with no branches, and they believe it has marks and paintings scrawled on it. You bring a flashlight, a notebook, a phone (they didn't have the budget for cameras) and some other helpful resources like water.
As you keep venturing through the tunnel, you get a deep sense of foreboding. You move into a place where the walls are more cleanly cut; eventually, you get to the end of the tunnel where there has been some scrawling and chipping. As you reach to write it down into your notebook, a computerized voice starts up behind you.
WARNING - DISTURBANCE DETECTED. SECURITY SYSTEMS ACTIVATED.
You turn around in shock and fear, then you hear a massive shake. You look carefully ...to find that boulders have blocked off your escape path. Turning around again, you realize that you're trapped in a cave with no where to go. You try to turn on your phone, but the Wi-Fi connection is zero. Immediately, you assume this is a big prank of some kind; that Joe guy was always smirking at you when you were digging, and there definitely was equipment up at the surface.
"Okay, cool! You got me, guys!" You yell, but your voice echoes and it becomes clear this is not only serious, but very puzzling; ...how did this primitive 'civilization' ever learn how motion detectors worked; let alone how to use a voice effect to mimic English, if it was a civilization at all?
But there's no time for wandering and pondering when you're probably going to suffer some horrible fate. You turn around to find that a flat vertical slab of rock has appeared.
In this slab of rock is embedded a colorful keypad (you found that out when pressing one of the letters gave you a beep):
There is also a large grid of letters haphazardly stitched into a wall:
What sequence of letters should you enter in the keypad?
Look carefully. Very carefully.
Removed grid-deduction because, while I assure you there is grid deduction involved, a lot of steps are required to get to it.
Look at the letters. Oh, and also look at the colors in the keypad.
There are two parts to this puzzle that are pretty much independent from each other; Both answers combine to make the solution.
Compare the letters in the keypad to the letters in the board. Notice the differences. Oh, and you need to look at a 7x7 grid.
You are playing around with colors, considering manipulating their hex components when your phone beeps, and you're suddenly able to contact someone appearing to be very concerned about you. "You've been lost for a week. We found your location but it appears to be surrounded with some sort of ultra-steel so we can't get to you...Oh, there's a keypad and grid? Can you take a picture and send it to me? Huh... it looks like something's hidden in the keypad. There are multiple representations of letters faintly under the ones in the keypad. Scrubbing off the uppercase Y in the keypad reveals a lowercase
y... yeah, I'd suggest using those letters instead for some of them. The w in the first row actually has one letter missing, by the way. You found little changes in color, so maaaybe since there's three changes, you could try a slitherlink or some sort? Oh, there's another part?...
...Attempting to match letters together doesn't feel right... ..The odd pixels. Comparing them with the background and doing something with the differences feels like the right way to go. Say, this is a 9x9 grid... And numbers on a 9x9 grid... Aha! The colors on the keypad. They could mean something - analyze their pixel colors, possibly their deviation from normal gray... 'prm2'? Maybe that could be a filter of some sort, I'm not sure. This is interesting-oh, sorry, I have an appointment to go to! See you later!"