I fixed the issue with getting stuck behind Aquamentus as well.
Fun story. I don't know if you read the about page on the site or not, but I originally wrote this code something like 17 years ago as a console application. Later I ported it to a web application. Some of the code had to change drastically, but there was a lot I was able to copy right over. Turns out that in the code that runs when the player gets hit and then determines where to move them, I never finished filling up a collection with all the places NOT to move the player to, including all but one of the enemy types. That bug exists in the oldest version of the code I still have, which means it's been there for 17 years. But it should be fixed now!