Hello everyone! Recently I looked into the source code of The Binding of Isaac v1.48 aiming for knowing how the game decides the location of Secret Rooms. After that, I found that understanding the source code really helps to find the Secret Room when playing the game. Tons of locations that I used to think being possible are in fact not possible to become the Secret Room. I summarized the knowledge into 5 simple rules that are easier to understand and remember, and now I am sharing them to all of you. I believe that at least parts of these rules are something new to most of you!
Note that what I show in this post is only a summary of the rules. There are a lot of details, pictures and examples about the rules in my PDF document on Google Docs, so if you are interested, watching my document is highly recommended.
Rule 1: Secret Rooms are never neighboring to the LEFT side of the Boss Room or the Top Secret Room.
Rule 2: Secret Rooms are never horizontally 4 rooms away from the Starting Room.
Rule 3: If the Secret Room neighbors only 2 rooms (the Top Secret Room does NOT count), then one of the 2 rooms must be at RIGHT side neighbor of the Secret Room. Also, this right neighboring room must be an End Room, as long as a very rare occasion does not occur (details in my document).
Rule 4: If the Secret Room neighbors only 1 room (the Top Secret Room does NOT count), then the neighboring room must be at RIGHT side neighbor of the Secret Room and must be an End Room, and the Top Secret Room must be neighboring to the Secret Room.
Rule 5: If you find a blank space that
1. meets the pattern shown in either of the two pictures (sorry it seams that it is not good to upload pictures on here, so please refer to my doc), AND
2. at least one of the two rooms marked by a letter ‘E’:
a) is an End Room AND
b) is not the Starting Room AND
c) does not neighbor to the Starting Room OR is a Special Room
then the space is not possible to become the Secret Room.
Again, if you are interested, please watch my document as there are pictures and examples that describe the rules better! The document is at https://drive.google.com/file/d/0B3jxLUI5Lb1rSUFTYk1jZ3Ruajg/edit?usp=sharing
The five rules are summarized from the source code, and I had checked them a lot by playing the game and watching Bisnap’s videos, so I believe that all the 5 rules are correct. But if you find a situation that rejects one of the rules, please contact me and show me, I’ll analyze it and improve the rules!
Feed backs are welcome! Thank you!