[alexfoo]

I disagree, the odd few are quite simple and can be done with pencil and paper.

https://adventofcode.com/2020/day/1 for example. It's not hard to do part 1 by hand.

You need two numbers from the input list (of 200 numbers) that add to 2020.

For each number n in the list you just have to check if (2020-n) is in the list.

A quick visual scan showed my input only had 9 numbers that were less than 1010, so I'd only have to consider 9 candidate numbers.

It would also be trivial for anyone who can do relatively simple things with a spreadsheet.