Fun idea to gameify some programming problems. I think the explanatory animations are great and give it an extra level of polish. I would gladly play through more levels of this.
My one line Python solutions (spoilers)
level1 = lambda s: ‘’.join(filter(str.isupper,s))
level2 = lambda s: f’{[*({*range(max(n:={*map(int,s.split())}))}-n)][1]}’