Thanks! Time constraints (and being generally busy) made it difficult to put in the story we wanted (and balance the gameplay) but we definitely had stuff in mind.
The main idea for me was to ensure you had to switch sides in order to win - balancing how many enemies you let past on either side and managing when you switch to keep one side from running away with the win.
Turns out though that's pretty complicated without playtesting and playtesters. The idea only really comes through in the 2nd and mostly 3rd level (which is significantly harder than the 2nd). Since they're much longer levels, there's more chances for enemies to slip by you to the point where it's inevitable.
The idea is that you *have* to let some enemies by, and it's a matter of minimizing it and ensuring that it's the team that's behind that you let by to keep things even. I don't think we quite accomplished that, but the 2nd and 3rd levels (though overly difficult) do a little bit