The sun makes it rather hard to play as vampires in the jungle; you can't really send them out until 9 PM, or else they'll burn. You gotta bring them home (or into a tent? do tents work? i had no tent with me) before the sun comes up, or else they'll burn. It's a challenge, really.
In return, they still have super speed and/or the bat/mist form, which makes it easy for them to move anywhere immediately. But that's really the only perk they have. They should definitely have some modified interactions, and dialogue; a vampire's heart shouldn't be "racing" because they're already dead.
And no, they would definitely not be immune to fire. The sun is a giant fireball, you know. And even if they have sun immunity, direct fire would still hurt them, just as it does with regular humans. They may be immortal and powerful, but they're also somewhat fragile in that way.
But they should be immune to, like.. things that require them to, say, breathe in order for it to hurt them. Such as poison, probably. They don't breathe and they don't feel the cold. But would they be immune to electricity? I'm not sure about that one.
I'm also pretty sure you already can't drown vampires in the pool; they simply do not spend any vampire energy on swimming, so they'll be able to stay there as long as they wish, right? At least if it's an indoor pool. They're immune to pools.
And the vampire bat attack is just kinda funny. "Why are you attacking me, don't you realize I'm one of you???"
I'd really love it if the vampire, if they have the bat form, would ALSO turn into a bat just to scare them off. No items required.
