I'm not sure if anyone else has posted this but I didn't see anything when I looked. So, there is a small bug with the Curse of the Golden Ratio: You cast it upon an enemy, hold a movement button (I don't know if this works with mouse click movement) and the monster doesn't move. He just sits there. Melting in to coins. Has anyone else noticed this or was it intentional?
Walking, mashing spacebar, and spamming spells all result in all monsters under effect of Curse of the Golden Ration being unable to move... so it seems to have this effect whenever your turn lasts for a very short time.
There's also a bug where the Curse remains on the tile after the monster had died, and it tends to happen if you abuse the said movement-lock bug. Has killed my a few times when trying to retrieve gold after killing something: it seems to be tied to a specific pile of gold which is not picked up by walking over it (but can be picked by clicking).
Nightmare Curse and I believe Recursive Curse can also be left on the field: probably all other DOT curses as well, but that's just extrapolation. When the enemy dies sometimes the curse will not be removed from the field, and anything stepping onto that tile afterward will be struck by it. This happens consistently (as in every cast) with sufficiently large enemy counts on the floor (such as by sitting in a shop, closing the door, and waiting for over 9k turns). That gold you can't pick up isn't because you can't pick it up; it's because the spell hits you and generates another coin stack after you've picked up the stacks on the square.
