* Treasure chest (beware of mimics) containing the above or XP directly
* Walls cost a random amount of HP (despite registering as 0 for adjacent counts) but grant a random amount of XP. I suspect that getting a good score requires getting lucky and hitting a low-HP high-XP wall early, to stretch your score just a little bit further
* There's a gnome(?) that costs 0 HP but gives 10 XP
* Once you find the scroll of anti-mine, you get a lot of XP from picking up the leftover mines
But yes, many games are unwinnable.