Ironically, I used this same tileset when I was working through the CS50 game development course (Zelda lecture). Good memories!
The tip on K below helped. The animation is a little long on that. For trapping slimes, players might want to do that a little quicker. Especially if a slime is already chasing them. Maybe just after the first animation? Just my opinion, of course.
Over all a fun little game. Nice work!