Main: A level where you are venturing outside your home and it begins to rain harshly before causing a flood ultimately causing you to have to return home before the rain over flows.
Secondary: The rain is Highly acidic and you must grab small objects to hold over your head as you go back to your home (MUST)
Secondary 2: A intro where it starts to rain and you are not prepared for the weather (Optional)
Tradeoff: Choosing between the three main factors I would choose optimization as making fluent, clear gameplay with a goal in mind is most important with this type of theme.