I beat it because I'm smart and took notes. I agree that Signal is an impressive 48-hour achievement, made in significantly less time than I needed to get this review written. The puzzle design is interesting, making the player not only find the right keys but also figure out where each key is and how it is encoded. I think it was a wise decision to respond to correct solutions by triggering dialogue and locking the door controls. Without that feedback, there would've been a lot more for the player to keep track of, perhaps too much. It does leave the puzzles open to brute-forcing, but players who resort to that have only themselves to blame.
The music and background art are appealing and quickly set a Myst-esque mood, drawing you into a a world of eerie splendor. Some of the graphics are unpolished, but I won't hold that against a game like this. It's a story that leaves a lot to the imagination, and the oddness of the puzzle mechanics also makes me lean toward interpreting the whole thing as a dream sequence. I'm not convinced that anyone would actually build a church like that, before or after the apocalypse.
The Conclusion: This game is worth a try, if you're up for a bite-sized adventure game that will require some lateral thinking.