Hey, thanks for playing! :D
a) You are right, some of the squares are too bright
b) While making the last two levels I have played with secret items. It all seemed obvious to me as I made the game, but I can very well see how it can seem random for you to be stuck on a level until you bump into some wall… In retrospect, it was probably a mistake to make the last two levels beatable only if you find the secret, on the other hand I think the levels are small enough to make that feasible, even if a wee bit annoying
c) The purple ‘key’ is supposed to be a keyhole for the cyan keys, actually! This is again me thinking something is too obvious when it is really ambiguous, especially given the keyholes have “key” written on them in bold letters… not exactly a good design decision