Being able to opt out of PvP would be nice; maybe let players leave the Arena listings (and prevent them attacking others) if it's been 24 hours since they initiated a PvP encounter.
The pools that kill both characters should be...I don't know, yellow or purple or something. Anything but the same green as the leaves on the level structures. :/ Can't see 'em.
Minor discrepancy: It shouldn't tell you "Trophies Saved" on survival mode if you didn't exit through a door; it doesn't actually save your trophies if you've banked but then fall.