Guys, there sort of is a bonus to attacking the enemy castle, certain arrows of yours will gain experience, like the fire arrow, though others don't, like the basic arrow.
Anyways, if you want extra experience for your flak and heal arrows, just attack ground targets with the flak and try healing uninjured people with the heal arrow.
Using the forward rocket thing (C) you can skip the boss entirely. Just stand on the right edge of the left platform, and wait until the boss comes near you, then rocket across to the other side when the monster thing's bullet won't drop on you. After that you can freely grab the super laser and take out the boss easily and get out of there.
There needs to be a better way to log back in, I clicked back and clicked continue, and realized I had to type in the same username again, but I forgot what I had entered.