Instead of hardcoding the "prize" type and then watching for that to be created, specify it in the level description. Also, instead of giving both Sokoban end levels 50:50 chance for either prize, bias the one that used to always have the bag of holding to now have 75% chance for that and 25% chance for amulet of reflection, with the other one having those chances reversed. So still 50:50 overall.
3.3 KiB
3.3 KiB