The project already has a working resistor ladder that allows multiple switches to work on one pin. My implementation is a bit unreliable though as I had limited understanding of it when I first implemented it.
This is why when I came across this post that offers a different resistor ladder I implemented it to see if it is better. To my disappointment, it didn't work. The values I was getting were wildly different from the supposed computations found in the post.
I later found out that it actually did work and turned out to be more reliable. Turns out that there was this buggy behavior in my code that made only my version worked. What happened was I designated one pin both as an input and output. There were no errors but the outcome was not correct.
I have since fixed this and applied the new resistor ladder to the circuit. It's now reliable and working great. The changes are now reflected on the github page.