Tool to help find hidden rooms?

[KuroOneHalf]

I finished the game last night and managed to get all keys except one by myself, by just using my level design intuition to strike at walls that seemed suspicious and sometimes finding hidden rooms that way, but in watching a speedrun I found out about some hidden rooms I had no idea existed. Are there tools in the game to help find these?

I have the Secret Eye passive shard which says will let you see secret walls, and I thought it might help with these, but I don't notice it having any effect. Like, for example the entrance to the room where the key of Celeste is located, I can't find any tell that there's a hidden room up there, aside from the random platform in the air. Is there a tool I missed perhaps?

[Sigma]

Do you have the shard turned on or at least to rank 9? It's the only thing in the game that helps detect breakable walls. And fyi, it's working, i'm sure you are using it the wrong way.
Otherwise use a map guide to locate what rooms you are missing.

[KuroOneHalf]

Seems I was using Secret Eye incorrectly. I thought all passive shards worked like the double jump, where it's active all the time. Turns out you have to select them manually for them to work. Welp. Nevermind me then. ;w;

[DarkCrusader1985]

Originally posted by Kuroonehalf:

Seems I was using Secret Eye incorrectly. I thought all passive shards worked like the double jump, where it's active all the time. Turns out you have to select them manually for them to work. Welp. Nevermind me then. ;w;

If you get them to rank 9 they work as a passive effect and you don't have to equip them anymore.

[DJDiceZ]

Fun fact: Carabosse familiar also points at secret walls.