i liked the puzzles, really like the original idea too!! but i think something went wrong. and that could just be me missing a step too lol, but the way i thought: get the key where its number matches the number on the lock.
but i tried it twice. first i needed 30, but the key that actually adds up to 30 didnt work. in my 2nd playthrough i needed 40. but none of the keys added up to 40.