It fits the theme because u must collect the red bois (there are bad) and dont collect the green bois (there are good)
that's merely a colour indicator based on cultural norms, not actual game design imo
And if u beat the level it litereally says "GAME OVER"
Because u Catch always the things u dont should catch (Ur green u catch red and if u are red u catch green so u dont do this what u should do and its "GAME OVER" but bc failure is progress u get to the next level. (srry for my english i´m german...)
