Thanks for playing! Yeah, it seems pretty universal that level 4 was too hard. The intent was to introduce a new mechanic, but going down to the relic and not solving it means you can't backtrack to do the pure platformer path. If I could go back, I would make the platformer path more obvious in this one.
Originally, the eyes didn't have any indication beyond eyes opening / screen darkening; the rays from one that is seeing the player was added very late. It would have been better in retrospect to do a faint line or something from each, but I hadn't figured that out with this unfamiliar engine.
I believe I misjudged in the relics. I wanted to lead from a simple relic for the first level of each act into simple ciphers through the remaining 4 levels. However, nobody has really been solving them as far as I have seen, so this must be too tough. Also, I shouldn't have made them one try per life (one player found this can be bugged past by hitting ESC and returning to the level).