(I am now in a rush to test as many games as possible to help, so please do not mind the cursory reviewing style.)
Ah, the first puzzle game for me in this game jam, I think!
"Everything may look stationary while in the light, but things around you will change and disappear when you point the light away." -> Hey, this reminds me of one of the mechanics in "Outer Wilds". :) (Did not play it, but (unfortunately) spoiled it a bit to me by watching some parts…) The concept seems super cool even before playing! :)
Controls are QWERTY-only instead of layout-independent (I have an AZERTY keyboard), BUT arrow keys are enabled.
Upper-left message: even once disappeared, I can still read it; is this expected, or a bug?
I like the sounds! :) Sober, yet atmospheric. (Title screen, footsteps.)
Lower-left angel(?) statue: its colour makes it hard to distinguish on the floor! I would advise making it stand out more (either changing a colour, or adding some outline, or as you wish). By the way, this reminds me of "Doctor Who"’s Weeping Angels! Creepy! :S (Never watched the series, but I have seen the concept.)
Creepy musically-screamy sound!! :o (Before the two skulls.)
… All right, already stuck. XD
Oh, seeing PerIta Soft’s comment on fullscreen (and not reading more, not to spoil myself): so THIS might be the problem!! I was wondering right before why there were no side walls!! :o
Still totally stuck! ._. Spoiler: apart from the paper, nothing changes in the room…
Spoiler: Ah, maybe audio clues? Because the creepy sound strikes again.
First room: Ah, finally made it!! The worst thing is that I had thought of this early on, but was then led astray. XD Spoiler: by the elements.
Solved the 2nd room super rapidly, on the contrary! XD
Ah, small bug: in the 3rd room, looking back at a statue, I saw it switch between two states.
Spoiler: The creepy sound is apparently random (or cyclic), at least unrelated to what is happening.
Dealing with the statues in the 3rd room seems hard (although the objective is clear)… Am I missing something again?
I managed to deal logically with it and achieved the sequence, but nothing happened!
Ah, worked the second time! I think using the torch is a bit clunky at times; suggestion: let the player activate/deactivate it (using the left click, for example)! This may break some of the later puzzles, but for this one, it would have been great.
Four-light room: SOLVED!! :D Rather proud of me on this one! ^^ Still, once again, I think the possibility of deactivating the torch would have helped (I blundered once because of this, I feel this is a playability issue).
Spoiler: Next room: what?! I could open the door right away! :o Did I get something right by "chance" (I would say I was unlucky, there!)? <:o Oh, seeing the final sentence, this was entirely normal and a joke!! XD
Takeway: excellent concept (totally related to the constraint), and great variety in the puzzles presented here! :) I also like the sobriety of the sound effects, with no music (apart from the creepy ambience sound which kicks in from time to time!); this gives an immersive dungeon when coupled with the pervasive darkness… (As a coincidence, I just played "Imsomed" before, which is also based on darkness and light!) My ONLY criticism would be about playability (I offer my suggestion of a deactivable torch as a possible solution). As for difficulty, this is often hard to judge for puzzle games, as it depends on how much you want; maybe just have the first room a bit easier, [SPOILER] by removing the elements from inside.
Great idea, thanks you for the game (prototype?)! :) "I will upload a video of my process in making the game on my channel in the near future." -> Looking forward to it! :)