halo2-tutorial VS halo2-examples

As another example, you could define a circuit for proving the N-th Fibonacci number, where row i of the matrix has the values x[i-2], x[i-1], x[i]. This means you'd need three advice columns to begin with, let's call them a, b, c. Then, you'd constrain c to be equal to a + b in the same row using a gate, which requires adding a selector column for controlling it. And you'd have to set up equality constraints so that a and b are equal to b and c from the previous row. Last, in order to expose the N-th number as a public value, you'd need an instance column, constrained to equal the value of c at the last row.

To me, Halo2 had the steepest learning curve by far. Not just because of having to understand how PLONKish arithmetization works to build the circuits, but mostly because I found Halo2's API quite complex and its documentation hard to find. There are also few resources for learning Halo2: the best I found were the 0xparc course which provides a few really valuable code samples, as well as the examples in the main repo. You may also want to check out awesome-halo2 for updated resources.