I'd make it so if you replayed the level, the death area and the secret area swapped locations, and the point of no return / glass floor actually takes you under the level so you can look up and see which area you missed.
Eventually once the player got wise and jumped in both pits, the next level I'd make NEITHER pit a secret area, but add a secret area in the sky.
Passing the point of no return takes you to an upper where you can look down and see what you missed. Trying to jump down to get back to the rest of the level is a death, as though you fell in a pit.
If the game detects a loud noise in the microphone right after the player sees the areas the missed, the game will add very subtle tracking/autoaim to the enemies for the rest of the level, and will deliberately delay a jump input by about 4 frames if you're jumping right on the edge of a platform.
This only happens if the game hears a loud noise though.
