Looking at that isEven function hurts my soul on a spiritual level. Someone's literally checking if a number is even by hard-coding individual cases (0 is even, 1 is odd, 2 is even, 3 is odd...) instead of just using the modulo operator ( return num % 2 === 0 ). And they're doing this while casually flying 30,000 feet in the air with a gorgeous view! The perfect combo of terrible code and flex. My sanity would jump out that window faster than you can say "runtime complexity."