the lack of instructions was a deliberate choice for two reasons.
1. I took a try at making a game which is intuitive enough that you dont need them. Except for the two hotspots in defensive towers, my guess is rest is figurable easily enough.
2. There was also thematic/story reason for this. Apprentice works through faith. Everyone else thinks this is all there os, while the Apprentice believes there is more since the book says so. So he by faith believes and decides to act upon what the book says, and therefore he also encounters things that others have forgotten / ignore to exist, and have to figure out hinself how to deal with them.
Therefore also the player, who too is one of those who have forgotten the existence of colors and light, will have to figure these new things out.
You could say that through acting in faith you receive light to thing, which reveals new things.