Comment by fmbb

The ”core logic” of a program is what output it yields for a given input.

If you find a bug, you find it because you discover that a given input does not lead to the expected output.

You have to find all those ifs in your code because one of them is wrong (probably in combination with a couple of others).

If you push all your conditionals up as close to the input as possible, your hunt will be shorter, and fixing will be easier.